“MGM” are the famous initials of Metro-Goldwyn-Mayer, one of the oldest and most famous of all Hollywood movie studios.
 
Three large Wall Street investment banks—Merrill Lynch, Goldman Sachs and Morgan Stanley—were dubbed “MGM’ by at least 2000. Merrill Lynch was bought by Bank of America in 2008 and the fate of the “MGM” label is uncertain.
 
 
Wikipedia: Metro-Goldwyn-Mayer
Metro-Goldwyn-Mayer Inc., or MGM, is an American media company, involved primarily in the production and distribution of films and television programs.
 
MGM was founded in 1924 when the entertainment entrepreneur Marcus Loew gained control of Metro Pictures, Goldwyn Pictures Corporation and Louis B. Mayer Pictures. Loew combined them into a new film company with Mayer as its head of production. The newly formed Metro-Goldwyn-Mayer was intended to provide quality feature films for the Loew’s Theatres chain and was wholly owned by Loew’s Incorporated.
 
From the end of the silent film era through World War II, Metro-Goldwyn-Mayer was the most prominent motion picture studio in Hollywood, with the greatest output of all of the studios: at its height, it released an average of one feature film a week, along with many short subjects and serials. A victim of the massive restructuring of the motion picture industry during the 1950s and 60s, it was ultimately unable to cope with the loss of its theater chain – due to the U.S. Supreme Court decision United States v. Paramount Pictures, Inc. (1948) – and the power shift from studio bosses to independent producers and agents.
 
On April 8, 2005, the company was acquired by a partnership led by Sony Corporation of America and Comcast in association with Texas Pacific Group (now TPG Capital, L.P.) and Providence Equity Partners. MGM Mirage, a Las Vegas-based hotel and casino company listed on the New York Stock Exchange under the symbol “MGM”, is not currently affiliated with Metro-Goldwyn-Mayer.
 
Sony Pictures currently distributes MGM/UA and Columbia TriStar co-productions— including the recent Casino Royale—but outside of the co-productions MGM is now actively involved in acquiring worldwide film rights and distributing theatrical motion pictures in the United States. 20th Century Fox is handling the international theatrical distribution and worldwide home video distribution of MGM titles, excepting those which Sony Pictures acts as majority partner.
 
Established in 1924, MGM is tied for the fifth-oldest movie studio in history with Columbia Pictures. The studio’s motto, “Ars Gratia Artis”, is Latin meaning “Art for art’s sake.”
     
Wall Street Journal (February 22, 2000)
Market-Structure Debate Embroils Street;
Lawmakers Courted on Trading Issues
By GREG IP, MICHAEL SCHROEDER and CHARLES GASPARINO | Staff Reporters of THE WALL STREET JOURNAL
(...)
In Washington, lobbyists for some opposing brokers refer disparagingly to the big three firms as “MGM”—Morgan Stanley, Goldman and Merrill. 
     
Daily Telegraph (London)
ISSUE 1821 Saturday 20 May 2000
Germans doubt exchange deal
By George Trefgarne, Financial Correspondent
(...)
Mr Cox also accused three giant US investment banks Morgan Stanley Dean Witter, Goldman Sachs and Merrill Lynch, of attempting to push the deal through. City grandees have nicknamed the three “MGM” after the Hollywood film studio. 
 
Wall Street Journal (June 2, 2000)
Stock-Trading Powerhouses
Change Tune on Overhaul
By MICHAEL SCHROEDER | Staff Reporter of THE WALL STREET JOURNAL
(...)
A working group, led by Merrill Lynch & Co., Goldman Sachs Group Inc. and Morgan Stanley Dean Witter & Co., made waves earlier this year when its members submitted a confidential “white paper” to the Securities and Exchange Commission lobbying the regulator to bless a new electronically linked, national market system for U.S. stocks.
(...)
At a Senate Banking Committee hearing in February, the chief executives from the three powerful firms, which have become known on Wall Street as “MGM,” came under fire from competitors and some lawmakers who argued the proposal would tilt the system in the firms’ favor because the most powerful firms would effectively be building, running and overseeing the casino.
   
New York (NY) Times
Wall St. Primed For More Deals Like the Latest
By PATRICK MCGEEHAN
Published: August 31, 2000
(...)
A few years ago, Merrill, Goldman Sachs and Morgan Stanley were an unchallenged triumvirate known as ‘‘MGM’’ on Wall Street. But several changes have shaken up the ranks of investment banks: Morgan Stanley merged with the Dean Witter brokerage firm and grew much larger; Salomon Brothers merged with the Smith Barney brokerage firm and then became part of the Citigroup financial conglomerate, and Goldman Sachs went public and raised capital to finance its growth.
   
Daily Telegraph (London)
A ringing in the ears, but not in the cash till
Last Updated: 2:28pm GMT 21/03/2001
(...)
The tieless, suitless TMT teams at MGM - Morgan Stanley, Goldman Sachs, Merrill Lynch - are working frenziedly to restructure telcos’ balance sheets.
 
New York (NY) Times
A Tilt in Wall Street’s Pursuit of Private Equity
By JENNY ANDERSON
Published: April 20, 2007
(...)
But the so-called MGM triumvirate — Morgan, Goldman and Merrill — are going full steam ahead into private equity.
     
New York (NY) Times
Death and Near-Death Experiences on Wall St.
By JENNY ANDERSON and CHARLES DUHIGG
Published: September 20, 2008
(...)
At the time, Mr. Thain said he took the job because Merrill had the best wealth management business in the world and a premier investment banking franchise. Privately, he told friends that he wanted to resurrect the “MGM” days when Merrill, Goldman Sachs and Morgan Stanley dominated investment banking.