UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

SCHEDULE 14A

Proxy Statement Pursuant to Section 14(a) of the

Securities Exchange Act of 1934

(Amendment No.    )

Filed by the Registrant  ☑

Filed by a Party other than the Registrant  ☐

Check the appropriate box:

☐        Preliminary Proxy Statement

☐Confidential, for Use of the Commission Only (as permitted by Rule 14a-6(e)(2))

☐        Definitive Proxy Statement

☑        Definitive Additional Materials

☐        Soliciting Material Pursuant to §240.14a-12

MP MATERIALS CORP.

(Name of Registrant as Specified In Its Charter)

N/A

(Name of Person(s) Filing Proxy Statement, if other than the Registrant)

Payment of Filing Fee (Check all boxes that apply):

☑        No fee required.

☐        Fee paid previously with preliminary materials.

☐        Fee computed on table in exhibit required by Item 25(b) per Exchange Act Rules 14a-6(i)(1) and 0-11.

Your Vote Counts! *Please check the meeting materials for any special requirements for meeting attendance. Smartphone users Point your camera here and vote without entering a control number For complete information and to vote, visit www.ProxyVote.com Control # V29147-P01264 MP MATERIALS CORP. You invested in MP MATERIALS CORP. and it’s time to vote! You have the right to vote on proposals being presented at the Annual Meeting. This is an important notice regarding the availability of proxy material for the stockholder meeting to be held on June 11, 2024. Vote Virtually at the Meeting* June 11, 2024 8:00 AM Central Time Virtually at: www.virtualshareholdermeeting.com/MP2024 MP MATERIALS CORP. 1700 S. PAVILION CENTER DRIVE, SUITE 800 LAS VEGAS, NV 89135 Get informed before you vote View the Notice of Annual Meeting, Proxy Statement and 2023 Annual Report online OR you can receive a free paper or email copy of the material(s) by requesting prior to May 28, 2024. If you would like to request a copy of the material(s) for this and/or future stockholder meetings, you may (1) visit www.ProxyVote.com, (2) call 1-800-579-1639 or (3) send an email to sendmaterial@proxyvote.com. If sending an email, please include your control number (indicated below) in the subject line. Unless requested, you will not otherwise receive a paper or email copy. We encourage you to access and review all of the important information contained in the proxy materials before voting. 2024 Annual Meeting on June 11, 2024 Vote by June 10, 2024 11:59 PM Eastern Time

Vote at www.ProxyVote.com Prefer to receive an email instead? While voting on www.ProxyVote.com, be sure to click “Delivery Settings”. Voting Items Board Recommends V29148-P01264 THIS IS NOT A VOTABLE BALLOT This is an overview of the proposals being presented at the upcoming stockholder meeting. Please follow the instructions on the reverse side to vote these important matters. 1. Election of 2 Directors Named in the Proxy Statement Nominees: 1a. James H. Litinsky For 1b. Andrew A. McKnight For 2. Advisory vote to approve compensation paid to the Company’s named executive officers. For 3. The ratification of the appointment of KPMG LLP as the Company’s independent registered public accounting firm for the fiscal year ending December 31, 2024. For NOTE: The proxies are authorized to vote in their discretion upon such other business as may properly come before the meeting or any adjournment or postponement thereof.