Exhibit 5

March 31, 2006

Merrill Lynch & Co., Inc.

4 World Financial Center

New York, New York 10080

Ladies and Gentlemen:

We have acted as your counsel and are familiar with the corporate proceedings had in connection with the proposed issuance and sale by Merrill Lynch & Co., Inc. (the “Company”) of its senior debt securities (the “Senior Debt Securities”); and/or subordinated debt securities (the “Subordinated Debt Securities”, and together with the Senior Debt Securities, the “Debt Securities”), both of which may be convertible into common stock, par value $1.33  ¹/3 per share, of the Company (the “Common Stock”), preferred stock, par value $1.00 per share, of the Company (the “Preferred Stock”) or Depositary Shares representing Preferred Stock (the “Depositary Shares”); and/or warrants to purchase Debt Securities (the “Debt Warrants”); and/or warrants entitling the holders thereof to receive from the Company a payment or delivery determined by reference to decreases or increases in the level of an index or portfolio based on one or more equity or debt securities, any statistical measure of economic or financial performance, or the price or value of any commodity or any other item or index or a combination thereof (the “Index Warrants”); and/or warrants to receive from the Company the cash value in United States dollars of the right to purchase or to sell specified foreign currencies or units of two or more such foreign currencies (the “Currency Warrants”); and/or shares of Preferred Stock which may be convertible into Preferred Stock or Common Stock or exchangeable for Debt Securities; and/or shares of Preferred Stock which may be represented by Depositary Shares; and/or warrants to purchase shares of Preferred Stock (the “Preferred Stock Warrants”); and/or shares of Common Stock; and/or warrants to purchase shares of Common Stock (the “Common Stock Warrants”), in each case as shall be designated by the Company at the time of offering.

We have examined such documents and records as we deemed appropriate, including the following:

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The Debt Warrants, Index Warrants, Currency Warrants, Preferred Stock Warrants and Common Stock Warrants are hereinafter collectively referred to as the “Warrants”. The Warrants, Debt Securities, Preferred Stock, Depositary Shares and Common Stock are hereinafter collectively referred to as the “Securities”. The “1983 Senior Indenture” shall mean such indenture, as amended by the Trust Indenture Reform Act of 1990. The 1983 Senior Indenture, Subordinated Indenture and Index Warrant Indenture, including any supplemental indenture thereto, are hereinafter collectively referred to as the “Indentures”. The Debt Warrant Agreement, Currency Warrant Agreement, Index Warrant Agreement and Preferred Stock and Common Stock Warrant Agreement are hereinafter collectively referred to as the “Warrant Agreements”.

Based upon the foregoing and upon such further investigation as we deem relevant in the premises, we are of the opinion:

1. The Company has been duly incorporated under the laws of the State of Delaware.

2. The 1983 Senior Indenture and the Subordinated Indenture have each been duly and validly authorized, executed and delivered by the Company and, as amended by the Trust Indenture Reform Act of 1990 in the case of the 1983 Senior Indenture, constitute valid and binding agreements of the Company, enforceable in accordance with their respective terms.

3. When appropriate corporate action has been taken to authorize the Company to execute and deliver any applicable Index Warrant Indenture, supplemental indenture or Warrant Agreement, to fix the terms of one or more issues of Securities under an Indenture or Warrant Agreement and to authorize their issue, and such Indenture or Warrant Agreement shall have been duly executed and delivered by the Company and the trustee or warrant agent, and when the Securities with terms so fixed shall have been duly authenticated or countersigned by the trustee or warrant agent, as the case may be, and duly issued under the respective Indenture or Warrant Agreement in accordance with such corporate action, such Indentures and/or Warrant Agreements and such Securities will constitute valid and binding agreements of the Company, enforceable in accordance with their terms.

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4. When appropriate corporate action has been taken by the Company to fix the terms of one or more series of the Preferred Stock as contemplated in the Registration Statement, to authorize the execution and filing with the Secretary of State of the State of Delaware of a Certificate of Designations relating thereto and to authorize the issuance of shares thereof, and when such Certificate of Designations shall have been so executed and filed by the Company and Preferred Stock with the terms so fixed shall have been duly issued and delivered by the Company against payment of the consideration therefor or for Depositary Shares representing interests therein in accordance with such corporate action, such Preferred Stock will be validly issued, fully paid and non-assessable.

5. When appropriate corporate action has been taken by the Company to authorize the execution and delivery of a Deposit Agreement, and when such Deposit Agreement shall have been duly executed and delivered by the Company and the depositary, such Deposit Agreement will constitute a valid and binding agreement of the Company, enforceable in accordance with its terms.

6. When appropriate corporate action has been taken by the Company to authorize the issuance and deposit of Preferred Stock with a depositary pursuant to a Depositary Agreement and the issuance of Depositary Shares representing interests therein, and when such Preferred Stock shall have been duly issued and so deposited and such depositary shall have duly issued and delivered depositary receipts evidencing such Depositary Shares against payment of the consideration therefor in accordance with such corporate action, such Depositary Shares will represent valid interests in the Preferred Stock so deposited and shall entitle the holders thereof to the rights specified in the depositary receipts evidencing the Depositary Shares and in the applicable Deposit Agreement.

7. When appropriate corporate action has been taken by the Company to authorize the issuance of shares of Common Stock, such Common Stock, when issued, delivered and paid for as contemplated in the Registration Statement, will be duly authorized, validly issued, fully paid and non-assessable.

With respect to enforcement, the above opinions are qualified to the extent that enforcement of the Indentures, Warrant Agreements, Securities and Deposit Agreement may be limited by bankruptcy, insolvency or other laws of general applicability relating to or affecting enforcement of creditors’ rights or by general equity principles, and further to the extent that enforcement of any Securities denominated in other than United States dollars may be limited by requirements that a claim (or foreign currency judgment in respect of such claim) be converted into United States dollars at a rate of exchange prevailing on a date determined pursuant to applicable law. We have further assumed with respect to enforcement that, when fixed, the terms of the Securities will comply with all applicable “bucket shop” or similar state laws, or have the availability of federal preemption therefrom.

We consent to the filing of this opinion as an exhibit to the Registration Statement and to the use of our name wherever appearing in the Registration Statement and any amendment thereto. In giving such consent, we do not thereby admit that we are within the category of persons whose consent is required by Section 7 of the Securities Act or the related rules promulgated by the SEC.