<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2022-09-02</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0001801368</issuerCik>
        <issuerName>MP Materials Corp. / DE</issuerName>
        <issuerTradingSymbol>MP</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001290162</rptOwnerCik>
            <rptOwnerName>QVT Financial LP</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>888 SEVENTH AVENUE, 43RD FLOOR</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>NEW YORK</rptOwnerCity>
            <rptOwnerState>NY</rptOwnerState>
            <rptOwnerZipCode>10106</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>1</isOther>
            <otherText>Director by Deputization</otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

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                <value>Class A Common Stock</value>
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            </transactionDate>
            <deemedExecutionDate></deemedExecutionDate>
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                <transactionCode>S</transactionCode>
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            </transactionCoding>
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                <value></value>
            </transactionTimeliness>
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                    <value>43463</value>
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                <transactionPricePerShare>
                    <value>32.55</value>
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                <directOrIndirectOwnership>
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                    <value>Held by Fourth Avenue FF Opportunities LP - Series E</value>
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        <nonDerivativeTransaction>
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        <nonDerivativeTransaction>
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                <value></value>
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                    <value>Held by Saratoga Park Ltd</value>
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        </nonDerivativeTransaction>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Class A Common Stock</value>
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                <value>2022-09-06</value>
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                <value></value>
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                <transactionPricePerShare>
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                </transactionPricePerShare>
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                <directOrIndirectOwnership>
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                    <value>Held by Fourth Avenue FF Opportunities LP - Series E</value>
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        <nonDerivativeTransaction>
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                    <value>Held by QVT Family Office Onshore LP</value>
                    <footnoteId id="F1"/>
                </natureOfOwnership>
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        </nonDerivativeTransaction>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Class A Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2022-09-06</value>
            </transactionDate>
            <deemedExecutionDate></deemedExecutionDate>
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                <value></value>
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                <transactionShares>
                    <value>11377</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>31.59</value>
                </transactionPricePerShare>
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                    <value>D</value>
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                <directOrIndirectOwnership>
                    <value>I</value>
                    <footnoteId id="F1"/>
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                <natureOfOwnership>
                    <value>Held by Saratoga Park Ltd</value>
                    <footnoteId id="F1"/>
                </natureOfOwnership>
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        </nonDerivativeTransaction>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Class A Common Stock</value>
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            <transactionDate>
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                <value></value>
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                    <value>72877</value>
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                    <value>31.43</value>
                </transactionPricePerShare>
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                    <value>D</value>
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        <nonDerivativeTransaction>
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                <value>Class A Common Stock</value>
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                <value></value>
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                    <value>11934</value>
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                    <value>31.43</value>
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                <sharesOwnedFollowingTransaction>
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                <directOrIndirectOwnership>
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        <nonDerivativeTransaction>
            <securityTitle>
                <value>Class A Common Stock</value>
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            <transactionDate>
                <value>2022-09-06</value>
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                <transactionFormType>4</transactionFormType>
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                <value></value>
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                <transactionShares>
                    <value>59052</value>
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                <directOrIndirectOwnership>
                    <value>I</value>
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                    <value>Held by Saratoga Park Ltd</value>
                    <footnoteId id="F1"/>
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            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Class A Common Stock</value>
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                <value>2022-09-07</value>
            </transactionDate>
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                <transactionFormType>4</transactionFormType>
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                <value></value>
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                    <value>20471</value>
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                    <value>31.38</value>
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            <securityTitle>
                <value>Class A Common Stock</value>
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                <value>2022-09-07</value>
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                <transactionFormType>4</transactionFormType>
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                <value></value>
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                <transactionShares>
                    <value>3352</value>
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                    <value>31.38</value>
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                    <value>D</value>
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                <sharesOwnedFollowingTransaction>
                    <value>1171438</value>
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                <directOrIndirectOwnership>
                    <value>I</value>
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                    <value>Held by QVT Family Office Onshore LP</value>
                    <footnoteId id="F1"/>
                </natureOfOwnership>
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        </nonDerivativeTransaction>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Class A Common Stock</value>
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            <transactionDate>
                <value>2022-09-07</value>
            </transactionDate>
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                <transactionFormType>4</transactionFormType>
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                <value></value>
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                <transactionShares>
                    <value>16588</value>
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                    <value>31.38</value>
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                    <value>D</value>
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                <directOrIndirectOwnership>
                    <value>I</value>
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                    <value>Held by Saratoga Park Ltd</value>
                    <footnoteId id="F1"/>
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    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">QVT Financial LP and its general partner, QVT Financial GP LLC (together, &quot;QVT&quot;), may be deemed to have beneficial ownership over the 14,121,495 Common Shares held by Saratoga Park Ltd., QVT Family Office Onshore LP and Fourth Avenue FF Opportunities LP - Series E. The filing of this statement shall not be deemed an admission that QVT is the beneficial owner of the securities reported herein for purposes of Section 16 of the Securities Act of 1934, as amended, or otherwise. QVT expressly disclaims beneficial ownership of the securities reported herein except to the extent of its pecuniary interest therein. Fourth Avenue Capital Partners GP LLC is the general partner of Fourth Avenue FF Opportunities LP - Series E and may also be deemed to have beneficial ownership over the Common Shares held by Fourth Avenue FF Opportunities LP - Series E.</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>/s/ Meg Eisner</signatureName>
        <signatureDate>2022-09-07</signatureDate>
    </ownerSignature>
</ownershipDocument>
