Garish, ripe with hype, and at 7 1/2 hours, longer than any MGM movie except Erich von Stroheim's original version of Greed, MGM: When the Lion Roars is nonetheless almost ridiculously entertaining tune in at any point and you're bound to get hooked. A history of the Metro-Goldwyn-Mayer movie studio from 1924 to 1986 spread out over three nights, When the Lion Roars offers full-scale profiles of MGM legends including Greta Garbo, Clark Gable, and Judy Garland plus amusing commentary from former MGM stars ranging from Helen Hayes to Mickey Rooney. There are marvelous behind-the-scenes snippets such as a 1931 in-house promotional film about the Christmas party MGM threw for child star Jackie Cooper. And running beneath all the vintage film clips and the glamour, you hear the stories of the tough businessmen who created and ran this entertainment empire.
It's a fun seven hours plus; the trick is making it past each night's first five minutes. Patrick Stewart (Star Trek: The Next Generation) is this project's host and narrator. Billed, as if he were a character, as ''The Master of Ceremonies,'' Stewart has been transformed into M.C. Fop: He begins each episode dressed in an ascot and silk smoking jacket, murmuring rapturously about ''this shadowland of make-believe,'' crowing about how MGM was ''a turbulent kingdom with its own rules its own mythology!''
Working from a script provided by Michael H. Wilson, Keith R. Clarke, and director Frank Martin, the usually charming Stewart is required to blather on like this throughout the entire series (''As the guns of the Second World War fall silent, MGM is more than ever the envy of Hollywood!''). But much of the time, this treacle doesn't matter, because the movies Stewart is cheerleading for are so enthralling. There are scenes from all the MGM films you'd expect, from Ben-Hur to The Wizard of Oz to Gone With the Wind; but there are also crisply edited samplings from less well known MGM productions a surreally lovely flop like The Kissing Bandit (1948), and a highly praised but now-neglected film like William Wellman's WWII saga, Battleground (1949).
There's certainly a sense in which When the Lion Roars is just one long, glitzy commercial: Turner Broadcasting, which runs TNT, is also the owner of the MGM film library; lots of the classics saluted here are shown regularly on TNT. Then, too, the previous credits of director Martin consist most prominently of things like The Making of ''RoboCop'' and The Making of ''52 Pick- Up'' promotional movies-about-movies so Martin really knows how to plug product.
There are few revelations, nothing that any film buff won't already know. What little analysis or criticism of the studio there is comes from the interviewees, not the narration. Helen Hayes, for instance, refers to the powerful Louis B. Mayer, MGM studio chief for 27 years, as ''a courtly, polished, evil villain He was a just a gentle, soft-spoken man. But he was evil.'' It's a pretty amazing sight the eternally gracious First Lady of the Theater rounding viciously on her former, famously autocratic boss.
But When the Lion Roars is essentially a conservative, paternalistic film; it's on the side of the studio and the businessmen. In a section set in the early '50s, Stewart says with enormous regret in his voice, ''the seemingly in destructible studio system'' the common practice of signing many of a studio's creative artists to long-term, exclusive contracts ''has begun to crumble.'' The notion held by many actors, writers, and directors that the studio system was creatively constraining as well as an economic anachronism is made to seem like a rather selfish, petty complaint.
But all nostalgia is essentially conservative, a yearning for fonder, more orderly times. Watching When the Lion Roars, you'll remember that there was a time when hearing the lazy growl of Leo the Lion at the start of a picture heralded the distinct possibility that you were about to see something special. Summoning up those feelings makes When the Lion Roars special as well. A-