Time to take it back from the droogs.

"The Freed Unit & the Golden Age of the MGM Musical," through July 24 at Film Forum, 209 W. Houston St. (betw. 6th Ave. & Varick St.), 212-727-8100.

Gene Kelly changed rain forever.

His song starts plain: do-do-do-do do-di do-do do-do-do do-do while he saunters down the soggy sidewalk, hat pulled low on his head like a tramp's, umbrella slung over his shoulder like the stick on which a bundle would swing, his face tilted upward because the sun's in his heart and he's rea-aaa-dy for love.

He jigs up and down the sidewalk, tapping all the way. His body travels in one piece-no wafting and bending at the bullish neck or the brawny arms, because this is no fancy-pants dancer but a stiff, a working stiff. The feet, however, are as quick and light as a bunny's and his slouchy shoulders keep morphing him into your favorite cartoon character. He hippity-hops in and out of the gutter, leaps over his flying feet, whirls in a wide waltz with an open umbrella and, in a splashy finale, stomps up and down in a vast puddle. He has no steps for this much joy.

Film Forum's multimovie extravaganza, "The Freed Unit and the Golden Age of the MGM Musical," which runs through July 24, features Kelly prominently (as well as a skinny Frank Sinatra, Judy Garland, the sweet French pixie Leslie Caron, a by-now wispy Fred Astaire, the mannequin with the mile-long legs Cyd Charisse, and mostly very smart-or deliciously dopey-scripts and songs). Kelly plays various roles: sailor on 24-hour leave in On the Town (1949), vaudevillian-cum-shortstop in Take Me Out to the Ball Game (1949), struggling painter in An American in Paris (1951), silent-film star at the dawn of the talkies in Singin' in the Rain (1952). But he has a single aim: to invent the steps for one kind of joy or another.

In Singin', for example, there's the joy of erasing from public memory the lousy youth you spent on the makeshift stages of tiny towns, clattering around in a checkered suit and sawing on a violin. There's ganging up with your best friend on the speech coach who's been assigned to teach you tongue twisters. There's wooing the girl you'd do anything for-before a painted sunset, with an ersatz breeze-because she knows what a phony you are. Kelly understands that we associate dancing with the pursuit of happiness, or at least glee. So he delivers as many variations on that high as he can drum up.

He can pull off this potentially cheesy enterprise because he's not one thing, but an incongruous bundle: sexy and clownish, down-to-earth-his bowlegs often bent-and lithe, musical and muscley (with the handsomest butt in motion-picture history, as the costume department makes abundantly clear). Kelly is a tender lover, but his virile avidity for the spunky women he pursues wrings the excess sugar out of the romance. He dances cheek-to-cheek, but also thigh-to-thigh and mouth-to-mouth. (Given the prudish decency codes at the time, Kelly gets away with a lot). He feels for the woman's pulse, rhythmic and otherwise, and she quickens to him-glad and avid, too.

Singin' in the Rain, released in 1952, was Kelly's last hit. (He was 39.) It marks the end of a movie tradition that includes Charlie Chaplin and the Marx Brothers, in which verbal and visual wit run hand in hand. By the late 50s, musicals had lost their acerbic edge and ingenious physicality. They'd grown at once more bloated and less substantial, the fluffy antithesis of the new lean hyperrealism of Brando and Dean.

The Kelly musicals seem to know they're in trouble. Their creators and the stars' silver-screen alter egos-the Coney Island hoochy dancer, out-of-work composer, itinerant magician, stuntman who wants to play Hamlet-worry incessantly that they have the wrong kind of artistic aspiration. They also secretly hope that if they push their hack work far enough, with gusto, it will end up as art.

It does. The evidence is the movies themselves, which work by the same principle. But the MGM crew doesn't entirely trust the evidence. Every picture is encumbered by at least one grimly cheery song-and-dance number, like "Make 'em Laugh" in Singin' in the Rain, that wants to get it through our thick skulls that being funny is a lot of work. Then there are those dreamy odes to high art, in which the female lead stumps along on pointed shoes like a pirate on a wooden leg.

Kelly and company worry we won't take them seriously. Well, we don't. That's why we love them. They don't require us to.