"Heavy Metal" is one of the worst ideas ever to be translated into a movie. For the uninitiated, Heavy Metal magazine is a glossy "aduly" publication of fantasy, horror and sex, built around "panel art" that aspires to a place somewhere between comics and fiction. The animated movie that opened yesterday brings together seven magazine scenarios, tenuously connecting them under a $9-million budget. If this were a government project, you could hear Sen. Proxmire howling all the way to Uranus.

The long list of discredits that runs at the end of the movie speaks for itself. Never have so many (70 animators from 14 countries and over 1,000 artists) contributyed so little in the name of commerce. Like its glossy inspiration, the celluloid "Heavy Metal" is an unwieldy mishmash of conflicting styles, a busy big-screen version of "Johnyy Quest," "The Super Seven," "Plasticman" and "Thundarr," all of which can be seen for free on Saturday mornings. The major difference, of course, is "Heavy Metal's"s abusive violence and banal sex. It's as it the animators had all studied at the Ralph Bakshi School of Animation Excess . . . and flunked.

Only two segments stand out, and those just barely. Mike Ploog's savage skeletons in "B-17" are so stupid and weird that they have their own obvious charm. "Den," based on Richard Corben's quintessential fantasy hero, finds young gangly Dan transformed into musclebound Den and transported to a strange planet where he's caught in a power struggle between a sorcerer and a queen-priestess. Here and in "So Beautiful and So Dangerous" (based on an ongong strip by Angus McKie) the filmmakers display minimal wit in the dialogue, but most of the stories lack even this grace. Mostly it's slap and dash, crush and crash, mish and mash, flip and flash.

Unfortunately, "Heavy Metal's" appeal must rest on its visuals and these are at best mediocre. One senses the filmmakers have been watching too many Levis commercials, Bakshi films and kidvid when they should have been watching Rene Laloux's "Planet Sauvage" or the visionary animation comint out of Eastern Europe. The primary movements are jerky, the backgrounds and landscapes are often murky or undistinguished, and the soundtrack is junked up with smatches of rock melodies that will constitute a best-selling soundtrack that has nothing to do with the film. Most irritatingly, the viewer's imagination is held squarely in check by the filmmakers' consistently puerile sex and death fantasies.

Oh, yes, there is an evil monster-spirit, a glowing green ball that caroms through "Heavy Metal" as if its episodes were bowling balls from hell. Moviegoers may wish they had consulted a crystal ball before throwing their good money after this bad movie. They probably would have seen a better show, even if it was only their own reflection.