#1POLYMET MINING Investor Presentation Minnesota Commitment | Global Opportunity December 2022#2Investor Presentation Minnesota Commitment | Global Opportunity Cautionary Notice POLYMET MINING This presentation contains certain forward-looking statements concerning anticipated developments in PolyMet Mining Corp.'s ("PolyMet") operations in the future. Forward-looking statements are frequently, but not always, identified by words such as "expects," "anticipates," "believes," "intends," "estimates," "potential," "possible," "projects," "plans," and similar expressions, or statements that events, conditions or results "will," "may," "could," or "should" occur or be achieved or their negatives or other comparable words. Forward-looking statements relate to future events or future performance and reflect management's expectations or beliefs regarding future events including, but not limited to, statements regarding the ongoing development of PolyMet's North Met Project and the results of the feasibility study on the permitted base case for the North Met Project, exploration results and budgets, reserve estimates, mineral resource estimates, continued relationships with current strategic partners, work programs, estimated capital and operating costs and expenditures, actions by government authorities, including changes in government regulation, the market price of natural resources, estimated production rates, ability to receive and timing of environmental and operating permits, estimated construction costs, job creation and other economic benefits, anticipated benefits of the proposed 50/50 joint venture between PolyMet and Teck (the "Joint Venture"), the company's expectations with respect to the future development of NorthMet and Mesaba and required financings, or other statements that are not a statement of fact. In addition, and for greater certainty, the results of the feasibility study on the permitted base case of the North Met Project constitute forward-looking information, and include future estimates of internal rates of return, net present value, future production, estimates of cash cost, proposed mining plans and methods, mine life estimates, cash flow forecasts, metal recoveries, and estimates of capital and operating costs. Forward-looking statements address future events and conditions and therefore involve inherent known and unknown risks and uncertainties. Such risks and uncertainties include, but are not limited to, among other things, adverse general economic conditions, operating hazards, inherent uncertainties in interpreting engineering and geologic data, fluctuations in commodity prices and prices for operational services, government regulation and foreign political risks, fluctuations in the exchange rate between Canadian and US dollars and other currencies, as well as other risks commonly associated with the mining industry. Specifically with respect to the Joint Venture, risks and uncertainties include risks relating to the parties meeting their conditions precedent, receipt of regulatory approvals, timing of closing the Joint Venture, the outcome of the development of the Mesaba project, Mesaba's actual reserves and resources could be lower than estimates, risks related to metal prices, interest rates and global economic conditions, and the outcome of any financing required to raise the funds for PolyMet's share of the initial work program and Glencore's funding commitment. Actual results may differ materially from those in the forward-looking statements due to risks facing PolyMet or due to actual facts differing from the assumptions underlying its predictions. No obligation exists to update this presentation. Unless otherwise stated, the information contained in this presentation is provided as at the date of this presentation and is subject to change without notice. PolyMet's forward-looking statements are based on the beliefs, expectations and opinions of management on the date the statements are made, and PolyMet does not assume any obligation to update (except as required by law) forward-looking statements if circumstances or management's beliefs, expectations and opinions should change. In connection with the forward-looking information contained in this presentation, PolyMet has made numerous assumptions, regarding, among other things, that the geological, metallurgical, engineering, financial and economic advice that PolyMet has received is reliable and is based upon practices and methodologies which are consistent with industry standards, and that the market prices for relevant commodities remain at levels that justify construction and/or operation of the North Met Project. While PolyMet considers these assumptions to be reasonable, these assumptions are inherently subject to significant uncertainties and contingencies. Specific reference is made to risk factors and other considerations underlying forward-looking statements discussed in PolyMet's most recent Annual Report on Form 40-F for the fiscal year ended December 31, 2021, and in our other filings with Canadian securities authorities and the U.S. Securities and Exchange Commission. PolyMet's financial statements have been prepared in accordance with International Financial Reporting Standards ("IFRS"). All amounts are in U.S. funds. No regulatory authority has reviewed or accepted responsibility for the adequacy or accuracy of this presentation. 2#3Investor Presentation Minnesota Commitment Global Opportunity Cautionary Note Regarding Mineral Resource Estimates POLYMET MINING Resources quoted are sourced from the Technical Report prepared under Canadian National Instrument 43 101- Standards of Disclosure for Mineral Projects ("NI 43-101") for PolyMet entitled "North Met Copper Nickel Project Feasibility Update," dated December 30, 2022, ("PolyMet Technical Report") as filed under the Company's SEDAR and EDGAR profiles, and the Technical Report entitled "Mesaba Project Form 43-101F1 Technical Report Mineral Resource Statement" ("Mesaba Technical Report") effective as of November 28, 2022, as filed on SEDAR and SEDAR. PolyMet Technical Report Proven & Probable Reserves are from Table 1-1 of the PolyMet Technical Report. Measured, Indicated, Measured & Indicated, inclusive of Mineral Reserves, and Inferred resources are from Table 1-2 of that same report. Mineral resources are not mineral reserves and do not have demonstrated economic viability. There is no certainty that all or any part of the mineral resources estimated will be converted into mineral reserves. A copper price of $3.16 per pound, a nickel price of $5.90 per pound, a cobalt price of $25.00 per pound, a palladium price of $1150 per ounce, a platinum price of $1,100 per ounce, a gold price of $1,450 per ounce and a silver price of $20.00 per ounce was used to estimate mineral reserves at the NorthMet Project. A copper price of $3.66 per pound, a nickel price of $6.78 per pound, a cobalt price of $28.75 per pound, a palladium price of $1,323 per ounce, a platinum price of $1,265 per ounce, a gold price of $1,668 per ounce and a silver price of $23.00 per ounce was used to estimate mineral resources at the NorthMet Project. Mineral reserves are estimated at an NSR cut-off of $9.39 per ton inside of the final pit design which includes the estimated plant operating costs (including rail handling costs), all G&A costs and the water treatment costs during pit operation. For a description of the key assumptions, parameters and methods used to estimate mineral reserves and resources, as well as data verification procedures and a general discussion of the extent to which the estimates of scientific and technical information may be affected by any known environmental, permitting, legal title, taxation, sociopolitical, marketing or other relevant factors, please see the PolyMet Technical Report. The scientific and technical information contained in this presentation regarding the North Met Project has been reviewed and approved by: Alberto Bennett, Daniel Neff, Daniel Roth and Laurie Tahija of M3 Engineering & Technology Corporation, Nicholas Dempers of SENET (Pty) Ltd., Thomas J. Radue and Jeff Ubl of Barr Engineering Co., Richard Schwering of Hard Rock Consulting, Herbert E. Welhener of Independent Mining Consultants, and Tad Crowie of JDS Energy & Mining Inc., who are all Independent Qualified Persons within the meaning of NI 43-101. Mesaba Technical Report The Mesaba Technical Report is preliminary in nature, includes inferred mineral resources that are considered too speculative geologically to have the economic considerations applied to them that would enable them to be categorized as mineral reserves, and there is no certainty that the mineral resources set out in the Mesaba Technical Report will be realized. Mineral resources that are not mineral reserves do not have demonstrated economic viability. There is no certainty that all or any part of the mineral resource will be converted into mineral reserve. It is uncertain if further exploration will allow improving the classification of the Indicated or Inferred mineral resource. The scientific and technical information contained in this presentation regarding the Mesaba Project has been reviewed and approved by: Andrew Ware, P.Geo. and a qualified person for purposes of NI 43-101. 3#4Investor Presentation Minnesota Commitment Global Opportunity Cautionary Note to U.S. Investors Concerning Estimates of Mineral Resources POLYMET MINING The mineral resource estimates described in this presentation have been prepared in accordance with the requirements of Canadian securities laws, which differ from the requirements of U.S. securities laws. The terms "mineral resource", "measured mineral resource", "indicated mineral resource" and "inferred mineral resource" are defined in accordance with NI 43-101 and the Canadian Institute of Mining, Metallurgy and Petroleum (the "CIM") - CIM Definition Standards on Mineral Resources and Mineral Reserves, adopted by the CIM Council, as amended. These definitions differ from the definitions in requirements under United States securities laws adopted by the United States Securities and Exchange Commission. Under Canadian rules, estimates of inferred mineral resources may not form the basis of feasibility or pre-feasibility studies, except in rare cases. Investors are cautioned not to assume that all or any part of an inferred mineral resource exists or is economically or legally mineable. An "inferred mineral resource" is that part of a mineral resource for which quantity and grade or quality are estimated on the basis of limited geological evidence and sampling. Geological evidence is sufficient to imply but not verify geological and grade or quality continuity. An inferred mineral resource has a lower level of confidence than that applying to an indicated mineral resource and must not be converted to a mineral reserve. It is reasonably expected that the majority of inferred mineral resources could be upgraded to indicated mineral resources with continued exploration. Investors are cautioned not to assume that all or any part of mineral resources determined in accordance with NI 43-101 and CIM standards will qualify as, or be identical to, mineral resources estimated under the standards of the SEC applicable to U.S. companies. Accordingly, information contained in this presentation may not be comparable to similar information made public by U.S. companies subject to the reporting and disclosure requirements under the United States federal securities laws and the rules and regulations thereunder. 4#5Investor Presentation Minnesota Commitment | Global Opportunity Executive Summary First mover along world-class Duluth Complex North Met project permitted for construction and operations (subject to litigation) Global decarbonization efforts create strong demand for our products Low-cost, long-life operation with attractive economics Significant expansion and exploration opportunities Glencore is our principal partner, a premier global mining company Recently announced joint venture with Teck Resources Limited (see Appendix A) 42 POLYMET MINING 5#6POLYMET MINING NORTHMET PROJECT 6#7Investor Presentation Minnesota Commitment Global Opportunity Ideally located CANADA Northshore T. Twin Metals Encampment T- Teck Arcelor POLYMET MININO BIWABIK IRON FORMATION MinnTac TUTac KeeTac HibbTac Wetlegs DULUTH COMPLEX Omi 10mi 20mi 30mi LAKE SUPERIOR Taconite DULUTH Copper-Nickel POLYMET MINING World-class copper, nickel, PGM resources located in the Duluth Complex District has 130 years of iron mining history Experienced labor, construction and supplier networks Established transportation and energy infrastructure Strong community and elected official's support 7#8Investor Presentation Minnesota Commitment | Global Opportunity Attractive Assets POLYMET MINING North Met Deposit 1 Proven & Probable Reserve: 289Mt Measured & Indicated Resource: 702Mt Inferred Resource: 441Mt Revenue distribution 2: Cu 53%, Ni 14%, PGM 29%, Co 2%, Au/Ag 2% Plant Site Previously processed 100k tpd taconite Primary crusher, ore transfer facilities and buildings will be refurbished Installed industrial electric power Tailings basin with over 300 Mt capacity Associated Infrastructure Rail connecting mine and plant Onsite access to class one rail carrier Plentiful water sources Established supplier network 1 Source: "PolyMet Technical Report" as filed under the Company's SEDAR and EDGAR profile. Additional resource and reserve information, including grades, is included on slide 20. 2 Based on payable metal in copper and nickel concentrates and metal price assumptions of $3.52/lb Cu, 8.13/lb Ni, $2,202/oz Pd, $975/oz Pt, $25.86/lb Co, $1747/oz Au. 8#9Investor Presentation Minnesota Commitment Global Opportunity Phased Development Phase I - Concentrate Northmet Animation-32K Option Phase II - Hydromet POLYMET MINING Develop 225M ton ore body LOM average strip ratio 1.36 Refurbish existing plant facilities Install new 40' SAG, ball and flotation circuit Upgrade existing tailings basin Produce copper and nickel concentrates Construct 1,000 tpd hydromet facility Finance with operating cash flows Improve metal recoveries Value-added products Nickel-cobalt hydroxide PGM precipitate Higher copper concentrate quality 9 Source: "PolyMet Technical Report" as filed under the Company's SEDAR and EDGAR profile. Additional resource and reserve information, including grades is included on slide 20.#10Investor Presentation Minnesota Commitment Global Opportunity Leverage Existing Plant Concentrate Loadout Hydromet Processing Addition 02 Concentrator Warehouse General Shops Crusher WTP Existing Facilities New Phase I Facilities New Phase II Facilities POLYMET MINING 10#11Investor Presentation Minnesota Commitment Global Opportunity Responsible Mining POLYMET MINING ENVIRONMENTAL STEWARDSHIP Design safeguards water, air and other natural resources Repurposes idled plant and addresses legacy water quality Among highest EPA rating of EIS of any mine in U.S. COMMUNITY COMMITTMENT Vested partner in Iron Range communities Aligned company and community values Strong support across business, labor and community spectrum 11#12Investor Presentation Minnesota Commitment Global Opportunity Key Project Metrics Phase I Mine life Project returns highly leveraged to metal prices 20 yrs NPV $M Mill feed 225m tons 1400 17% IRR Processing rate 32k tbd 1200 Annual metal produced¹ 97m lbs 1000 15% IRR Cash costs² 72 c/lb 800 Project capital $1,208M 600 12% IRR NPV / IRR $304M / 11% 400 Phase I & II 200 8% IRR Annual metal produced¹ 118m lbs 0 Cash costs² -11 c/lb -10% Project capital $325M Base Case Change in Metal Prices +10% +20% NPV / IRR $487M / 12% Source: "PolyMet Technical Report" as filed under the Company's SEDAR and EDGAR profile. Additional resource and reserve information is included on slide 20. Project metrics and sensitivities determined using metal price assumptions of $3.52/lb Cu, $8.13/lb Ni, $2202/oz Pd, $975/oz Pt, $25.86/lb Co, $1747/oz Au. 1 Total payable metal in copper and nickel concentrates shown on a copper equivalent basis. 2 Cash cost per pound of payable copper contained in concentrates, net of by-product credits. ■ PHASE II ■ PHASE I POLYMET MINING 12#13Investor Presentation Minnesota Commitment Global Opportunity Principal Shareholder - Glencore CANADA Rail to Canadian Smelters Rail to West Coast Great Lakes Shipping Experts in mine and processing operations Industry-wide support network Global scale and marketing capabilities Long-term source for Canadian smelters Geographically positioned for trading Offtake agreement Strong Financial Partner - Investments totaling more than $400M POLYMET MINING 13#14POLYMET MINING POSITIONED TO MEET GLOBAL DEMAND 14#15Investor Presentation Minnesota Commitment | Global Opportunity Global Growth In Electric Vehicles Electric Vehicle Sales (in millions) 54 Electric Vehicle Share of New Car Sales 58.0% 26 28.0% 8.5 10.0% 1.7 2.7% 2020 2025 2030 2040 2020 2025 2030 2040 Global EV Fleet 2020 8.5M 2030 Source: Bloomberg New Energy Finance estimates Global Vehicle Fleet 1.2B 2030 1.4B 2020 116M POLYMET MINING 15#16Investor Presentation Minnesota Commitment Global Opportunity Clean & Renewable Energy Metals To Support Transformation 节 s PolyMet Revenue Distribution¹ Key Drivers For Base Metals EV Growth: 58% of cars sold in 2050 will be EVs² Power Generation Energy Storage Systems Grid Related Projects Copper & Nickel Requirements³ 2020 2050 Copper 29 Mt 69 Mt +138% Increase Nickel 2.5 Mt 7.6 Mt +204% Increase Cu Pd Ni Co Pt Au/Ag 1 Based on payable metal in copper and nickel concentrates and metal price assumptions of $3.52/lb Cu, 8.13/lb Ni, $2,202/oz Pd, $975/oz Pt, $25.86/lb Co, $1747/oz Au. 2 Wood Mackenzie, Market Insights 2022 3 The Drive for Decarbonization Sept 2022 Metals & Mining Forum POLYMET MINING 16#17Investor Presentation Minnesota Commitment Global Opportunity POLYMET MINING Bright Copper Outlook Estimated Global Copper Supply/Demand Imbalance Mt 35 30 GNN & 25 20 Demand 15 Supply 10 10 Copper Shortfall Probable Projects Demand projected to exceed global production in 2026 onward Urbanization, electric vehicle growth and decarbonization efforts drive demand Supply gap due to reserve depletion, falling head grades and long lead times Our commodity mix is essential to building zero-carbon technologies 0 2000 2004 2008 2012 2016 2020 2024 2028 2032 2036 2040 Source: Wood Mackenzie, Global Copper Long-Term Outlook 2022 17#18Investor Presentation Minnesota Commitment Global Opportunity Shortfall in Long-Term Nickel Supply 250 200 150 100 Global Nickel Supply-Demand Imbalance alti Surplus Contained Ni 0 -50 -100 -150 50 (kt) 2010 Deficit 2012 2014 2016 2018 2020 2022 2024 Source: Wood Mackenzie, Global Nickel Long-Term Outlook 2020 POLYMET MINING ווי 2030 Demand projected to exceed global supply by 2028 China accounts for nearly 60% of total demand due to dominant position in stainless and accelerating demand for EV batteries By 2040, battery precursors will account for 37% of global nickel production 2026 2028 18#19POLYMET MINING MINERAL RESOURCE & OPPORTUNITY 19#20Investor Presentation Minnesota Commitment Global Opportunity Abundant Resource 20 Year Pit Shell Magenta Zone Unit 1 Footwall Mineralization 0 1000 2000 3000 POLYMET MINING Short Tons Copper Nickel Palladium Platinum Gold Cobalt Mineral Resource 1,2 (Millions) (%) (%) (ppb) (ppb) (ppb) (ppm) Measured 315 0.257 0.0769 240 68 35 72 Indicated 387 0.248 0.0725 229 66 33 68 Measured & Indicated 702 0.252 0.0745 234 67 34 69.8 Inferred 441 0.254 0.0701 243 67 34 55.4 Proven & Probable 3 289.1 0.29 0.084 270 79 39 74 1 See Table 1-2 and associated foot notes from the PolyMet Technical Report as filed under the Company's SEDAR and EDGAR profile. 2 Measured & Indicated resources are inclusive of Proven & Probable reserves. Additional information on Mineral Resources is included on slide 8. 3 See Table 1-1 and associated foot notes from the PolyMet Technical Report. 20#21Investor Presentation Minnesota Commitment Global Opportunity Regional Exploration Opportunity Wetlegs 1 NorthMet Serpentine 1 Mesaba 1 Undrilled up-dip exploration potential to SW and NE of Pit 1 Unclassified Mineral Resources: Non North Met mineralization solids based on public file information from MN Natural Resources Research Institute TR 2003/21. POLYMET MINING Feet 0 1250 2500 3750 5000 21#22POLYMET MINING SUMMARY 5 SMS 22#23Investor Presentation Minnesota Commitment | Global Opportunity Path Forward Final EIS Federal Permit¹ State Permits¹ Land Exchange 1Subject to litigation Project Finance 42 POLYMET MINING Commercial Production Construction (24-30 Months) 23#24Investor Presentation Minnesota Commitment | Global Opportunity Project Highlights Q1 Q2 Q3 Q4 PolyMet Copper C1 Cash Costs (1) Attractive Economics Robust demand for products Timed to meet supply deficit Long-life, low-cost asset Expansion Opportunity Existing infrastructure supports higher volumes Mine plan represents 1/3rd of existing M&I resource 441M tons inferred material Exploration Potential High grade, near mine, legacy intercepts Untested strike to NE and SW of ore body Glencore Strategic Alliance First Mover in Duluth Complex All key state and federal permits (subj. to litigation) ~8B tons of mineralized material in complex 2 1 Wood Mackenzie 2022 C1 by-product cost curve (Q3 2022). 2 Based on public file data (NRRI TR 2003/21) and public file company releases. 24 POLYMET MINING#25Investor Presentation Minnesota Commitment | Global Opportunity Capital Structure Shares Outstanding (TSX: POM, NYSE American: PLM) 101.5 million Market Capitalization US$292 million Cash Stock Price (Sept. 30, 2022) Stock Price 52-week range Financial information as of September 30, 2022 US$8.6 million US$2.75 US$2.41 $4.79 POLYMET MINING 25#26Investor Presentation Minnesota Commitment Global Opportunity Executive Leadership Jon Cherry President & CEO Leader in new mine development and environmental policy Executive roles in 20- year Rio Tinto career Permitted and developed Eagle Mine +30 years experience Pat Keenan Chief Financial Officer Extensive finance and executive leadership with major global mining. operations Finance executive at Rio Tinto and Newmont +30 years experience Denton Henkelman Project Director Extensive development and construction leadership at major mining projects globally including the Eagle nickel-copper and Diavik diamond mines, iron-ore expansions and ancillary facilities +35 years experience Andrew Ware Chief Geologist Authority on the Duluth Complex and Mid- Continent Rift Principal geologist with Rio Tinto developing projects in SE Asia and the Americas +30 years experience POLYMET MINING 26#27POLYMET MINING Appendix A: NewRange Copper Nickel LLC i#28NewRange Copper Nickel - Transaction Summary Poly Met Mining Corp & Teck Resources Limited to form 50:50 Joint Venture • Named NewRange Copper Nickel LLC . NEWRANGE COPPER NICKEL To develop the North Met project and study development of the Mesaba asset • NewRange Copper Nickel will responsibly deliver North American-sourced clean Management team comprised of PolyMet and Teck representatives energy metals • PolyMet and Teck will fund their pro-rata share of the newly formed JV . Glencore maintains 71% interest in and will provide financial support to Poly Met • Total assets form one of the largest clean-energy mineral resources in the US and globally • Definitive agreement announced July 20, 2022 (closing anticipated Q1 2023) POLYMET MINING#29NewRange Copper Nickel - Strategic Rationale • JV will assist in de-risking development of the North Met project • Teck's Mesaba resource(a) is located near PolyMet's North Met project • • PolyMet brings demonstrated strength in regulatory review and permitting in Minnesota Teck adds demonstrated experience in construction, operations and technology development · Glencore excels in processing, smelting and refining operations in North America • JV further demonstrates commitment to economic development in northern MN a) For more information on the Mesaba 2022 independent resource estimate, refer to the Mesaba Technical Report effective as of November 28, 2022, as filed on SEDAR. POLYMET MINING iii#30NewRange Copper Nickel - A Significant Global Mineral Resource • M&I resources of 702 million tons (Mt) • • and 2,207 Mt for NorthMet and Mesaba, respectively Further Inferred resources of 441 Mt and 1,423Mt, respectively Resources contain copper, nickel, cobalt, PGMs, gold, and silver Sources: PolyMet Technical Report dated December 30, 2022, as filed under the Company's SEDAR and EDGAR profiles, and the MesabaTechnical Report effective as of November 28, 2022, as filed on SEDAR NorthMet and Mesaba resources are estimated independently with differing underlying variables. Metal price decks are the same, metallurgical recoveries, pit slope variables and NSR cut offs are specific to each resource POLYMET MINING iv