UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM 8-K

CURRENT REPORT

Pursuant to Section 13 OR 15(d) of The

Securities Exchange Act of 1934

Date of Report (Date of earliest event reported): December 5, 2012

McMoRan Exploration Co.

(Exact name of registrant as specified in its charter)

Registrant’s telephone number, including area code: (504) 582-4000

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions:

Item 8.01 Other Events.

On December 5, 2012, McMoRan Exploration Co. (“MMR”), Freeport-McMoRan Copper & Gold Inc. (“FCX”) and Plains Exploration & Production Company (“PXP”) issued a joint press release announcing that FCX had entered into a definitive merger agreement with each of MMR and PXP. Subject to the terms and conditions of each merger agreement, FCX will acquire MMR for aggregate consideration of approximately $3.4 billion in cash, or $2.1 billion after adjusting for the 36 percent of MMR’s outstanding equity interests that are currently owned by FCX and PXP, and FCX will acquire PXP for aggregate consideration of approximately $6.9 billion in cash and stock. At the closing of the MMR transaction, MMR stockholders will also receive a distribution of units in a royalty trust which will hold a 5 percent overriding royalty interest on future production of hydrocarbons from MMR’s existing shallow water ultra-deep Gulf of Mexico properties.

The joint press release is attached hereto as Exhibit 99.1 and is incorporated into this Item 8.01 by reference.

Item 9.01 Financial Statements and Exhibits.

The Exhibit included as part of this Current Report is listed in the attached Exhibit Index.

CAUTIONARY STATEMENT REGARDING FORWARD-LOOKING STATEMENTS

This document contains forward-looking statements concerning the proposed transactions between FCX, MMR and PXP, the financial and business impact of such transactions, management’s beliefs and objectives with respect thereto, and management’s current expectations for future operating and financial performance, based on assumptions currently believed to be valid. Forward-looking statements are all statements other than statements of historical facts. The words “anticipates,” “may,” “can,” “plans,” “believes,” “estimates,” “expects,” “projects,” “intends,” “likely,” “will,” “should,” “to be,” and any similar expressions or other words of similar meaning are intended to identify those assertions as forward-looking statements. It is uncertain whether the events anticipated will transpire, or if they do occur what impact they will have on the results of operations and financial condition of FCX, MMR, PXP or of the combined company. These forward-looking statements involve significant risks and uncertainties that could cause actual results to differ materially from those anticipated, including but not limited to the ability of the parties to satisfy the conditions precedent and consummate either or both of the proposed transactions, the timing of consummation of either or both of the proposed transactions, the ability of the parties to secure regulatory approvals in a timely manner or on the terms desired or anticipated, the ability of FCX to integrate the acquired operations, the ability to implement the anticipated business plans following closing and achieve anticipated benefits and savings, and the ability to realize opportunities for growth. Other important economic, political, regulatory, legal, technological, competitive and other uncertainties are identified in the documents filed with the Securities and Exchange Commission (the “SEC”) by FCX, MMR and PXP from time to time, including their respective Quarterly Reports on Form 10-Q, Annual Reports on Form 10-K, and Current Reports on Form 8-K. The forward-looking statements including in this press release are made only as of the date hereof. None of FCX, MMR or PXP undertakes any obligation to update the forward-looking statements included in this press release to reflect subsequent events or circumstances.

IMPORTANT ADDITIONAL INFORMATION WILL BE FILED WITH THE SEC

In connection with the proposed transaction, the royalty trust formed in connection with the transaction will file with the SEC a registration statement on Form S-4 that will include a proxy statement of MMR that also constitutes a prospectus of the royalty trust. MMR, the royalty trust and FCX also plan to file other relevant documents with the SEC regarding the proposed transaction. INVESTORS ARE URGED TO READ THE PROXY STATEMENT/PROSPECTUS AND OTHER RELEVANT DOCUMENTS FILED WITH

THE SEC IF AND WHEN THEY BECOME AVAILABLE, BECAUSE THEY WILL CONTAIN IMPORTANT INFORMATION. You may obtain a free copy of the proxy statement/prospectus (if and when it becomes available) and other relevant documents filed by MMR, the royalty trust and FCX with the SEC at the SEC’s website at www.sec.gov. In addition, you will be able to obtain free copies of these documents by phone, e-mail or written request by contacting the investor relations department of MMR or FCX at the following:

PARTICIPANTS IN THE SOLICITATION

MMR and FCX and their respective directors and executive officers and other members of management and employees may be deemed to be participants in the solicitation of proxies in respect of the proposed transaction. Information about MMR’s directors and executive officers is available in MMR’s proxy statement dated April 27, 2012, for its 2012 Annual Meeting of Stockholders. Information about FCX’s directors and executive officers is available in FCX’s proxy statement dated April 27, 2012, for its 2012 Annual Meeting of Stockholders. Other information regarding the participants in the proxy solicitation and a description of their direct and indirect interests, by security holdings or otherwise, will be contained in the proxy statement/prospectus and other relevant materials to be filed with the SEC regarding the merger when they become available. Investors should read the proxy statement/prospectus carefully when it becomes available before making any voting or investment decisions. You may obtain free copies of these documents from MMR or FCX using the sources indicated above.

This document shall not constitute an offer to sell or the solicitation of an offer to buy any securities, nor shall there be any sale of securities in any jurisdiction in which such offer, solicitation or sale would be unlawful prior to registration or qualification under the securities laws of any such jurisdiction. No offering of securities shall be made except by means of a prospectus meeting the requirements of Section 10 of the U.S. Securities Act of 1933, as amended.

SIGNATURE

Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized.

Date: December 5, 2012

McMoRan Exploration Co.

Exhibit Index