三联金属有限公司美股招股说明书（2025-11-07版）

NewIssue November7, 2025 Up to US$200,000,000 of Common Shares This prospectus supplement (this “Prospectus Supplement”) of Trilogy Metals Inc. (“we”, “Trilogy” or the “Company”), togetherwith the base shelf prospectus dated October31, 2025 (the “Prospectus”), qualifies the distribution (the “Offering”) of commonshares (the “Offered Shares”) in the capital of Trilogy having an aggregate offering amount of up to US$200,000,000. See “Plan ofDistribution” and “Description of Share Capital”. Trilogy has entered into an equity distribution agreement dated November7,2025 (the “Distribution Agreement”) with CantorFitzgerald& Co., BMO Capital Markets Corp., Canaccord Genuity LLC, National Bank of Canada Financial Inc., and RaymondJames (USA) Ltd. (together the “Agents” and each an “Agent”), pursuant to which Trilogy may offer and issue the Offered Sharesfrom time to time through the Agents, as agents, in accordance with the terms of the Distribution Agreement. See “Plan ofDistribution”. The Offering is being made in the United States under the terms of the Company’s registration statement on FormS-3(File No.333-291209) filed with the United States Securities and Exchange Commission (the “SEC”). We had previously registeredcommon shares of the Company (the “Common Shares”) having an aggregate offering price of up to US$25,000,000, offered bymeans of a 424(b)(5) prospectus supplement, dated May 27, 2025 (the “prior prospectus supplement”). As of the date of thisprospectus supplement, we have sold Common Shares representing an aggregate amount of approximately $25,000,000 pursuant to theprior prospectus supplement under the prior equity distribution agreement (as defined herein). The offering pursuant to the priorprospectus supplement has terminated. No sales of our Offered Shares under this Prospectus Supplement will be made in Canada, to anyone known by the Agents tobe a resident of Canada or over or through the facilities of the Toronto Stock Exchange (the “TSX”) or any other exchange ormarket in Canada. Outstanding Common Shares are listed and posted for trading on the TSX and the NYSE American LLC (“NYSE American”), underthe symbol “TMQ”. On November6, 2025, the last complete trading day prior to the date hereof, the last reported sale price of ourCommon Shares on the TSX was C$5.66 per Common Share and on the NYSE American was US$3.97 per Common Share. The TSXhas conditionally approved the listing of the Offered Shares, subject to the Company fulfilling all of the requirements of the TSX andthe NYSE American has authorized the listing of the Offered Shares distributed under the Offering. Sales of the Offered Shares, if any, under this Prospectus Supplement and the Prospectus will be made in transactions that are deemedto be an “at-the-market offering” as defined in Rule415 under the United States Securities Act of 1933, as amended (the “U.S.Securities Act”), including sales made by the Agents directly on the NYSE American or any other trading market for the CommonShares in the United States or as otherwise agreed between the Agents and the Company. No sales of our Offered Shares under thisProspectus Supplement will be made in Canada, to anyone known by the sales agent to be a resident of Canada or over or through thefacilities of the TSX or any other exchange or market in Canada. Subject to the pricing parameters in an agency transaction notice, theOffered Shares will be distributed at the market prices prevailing at the time of the sale. As a result, prices at which Offered Shares aresold may vary as between purchasers and during the period of distribution. See“Plan of Distribution”. Trilogy will pay the Agents a commission for their services in acting as agents in connection with the sale of the Offered Sharespursuant to the Distribution Agreement (the “Commission”). The amount of the Commission shall not exceed 3.0% of the gross salesprice per Offered Share sold. In addition, the Company has agreed to reimburse certain expenses of the Agents in connection with theDistribution Agreement. The Company estimates that the total expenses required under the Distribution Agreement that it will incurrelated to the commencement of the Offering, excluding compensation payable to the Agents under the terms of the DistributionAgreement, will be approximately $200,000. See“Plan of Distribution”. The net proceeds that Trilogy will receive from sales of the Offered Shares will vary depending on the number of Offered Sharesactually sold and the offering price for such Offered Shares, but will not exceed $200,000,000 in the aggregate. See “Use of Proceeds”for how the net proceeds, if any, from sales under this Prospectus Supplement will be used. In connection with the sale of the Offered Shares on our behalf, the Agents may each be deemed to be an “underwriter” within themeaning of Section2(a)(11) of the U.S. Securities Act, and the compensation of the Agents may be deemed to be underwritingcommissions or discounts.