MGM and United Artists movies have started appearing on Apple's iTunes Store this evening. The new movies are listed amongst the New Releases (iTunes link) on iTunes.
Popular MGM Titles include (iTunes links) Mad Max, Bulletproof Monk, Rocky, Pieces of April, The Thomas Crown Affair, Dances with Wolves, and Robocop. Meanwhile, only one United Artists movie (Ronin) has been added so far.
United Artists and MGM have now joined Lionsgate, Paramount and Disney in selling movies on Apple's iTunes Store. With the release of the Apple TV, additional movie content for the iTunes Store has likely become a priority for Apple. When the iTunes Movie sales originally launched, Disney was the only studio that had participated. There had been rumors that Wal-mart and other retailers were threatened by Apple's entry into the movie-market. Even now, these new studio's movies appear to represent older "catalog" movies, rather than "new" releases.
An official press release from Apple should be expected later today.