There's nothing heavy or metallic about Heavy Metal (except for parts of the soundtrack), but it is a neat science fiction story. Stories, if you prefer---the movie is an amalgamation of the first 7 issues of the magazine with the same name.
I have wanted to see this movie since I saw the trailer for it when I was 9 years old, and when I found out that Columbia Pictures was releasing a "louder and nastier" version, complete with digital sound and a new print, nothing was stopping me this time. The movie has in some ways set the standard for later Japanimation (aka Anime), and has gained a cult following over the years. I have to wonder though, how much of the attraction to Anime is based on Japan's open acceptance of nudity and American fascination with sex.
The plot is simply a series of short stories, where an evil entity called the Loch-nar unleashes a pass of destruction where ever it goes. The Loch-nar well earns the title of being one of the most insidious villains in animation history. The music is excellent---Elmer Bernstein's compositions complements the rock and metal music in the soundtrack (which include Blue Öyster Cult, Black Sabbath, and Devo). Unfortunately, I fear the sequel (which is supposedly in the works), will lack such innovation in both the animation and the music.
This is definitely worth checking out if you're into novel animation and hard music.