I haven't seen Heavy Metal since I was a kid, but my opinion wasn't very favorable then. But, this is the same kid who worshipped Wizards, which these days I think is almost unwatchable
I will respond to this with a copy-and-paste of my "write-up" from September (it's mostly pictures).
Well. I grew up in the era of Sex and Drugs and Rock 'n' Roll and I saw this movie when I was just starting to hit puberty and I can tell you that it was about the greatest thing in the World. I'm sure it's not nearly so popular now and I have no idea how a contemporary audience would see it but I can't not appreciate it for the go-for-broke, end-of-the-70s, adolescent male fantasy that it is.
When a glowing green orb called the Loc-Nar is brought back to Earth from a trip to space, it quickly reveals itself to be "The Sum Of All Evil".
Cornering a young teenage girl it informs her that it must destroy her as she may be the last thing that can destroy it. First, it wants to show her what it is and thus begins the omnibus of Sci-Fi/Horror/Fantasy tales that makes up the bulk of the film. The Loc-Nar takes us from future dystopian New York to another planet in a more medieval and fantastic time, then a trial gone-awry on a space-station, to a World War II bomber, an accidental alien-kidnapping at The Pentagon, and finally to our climactic story of Good versus Evil on a fantasy world of magic, mutants, lasers, and legend.
Along the way we'll be treated to robots, disintegrations, double-crosses, beheadings, lasers, swords, guns, fantastic worlds, space, drugs, space-flights on drugs, mutants, giant bats, even zombies, lots of death, and of course, plenty of nudity and sex.
Yeah, it's just 90 minutes of all that, laced with a kick-ass soundtrack of Blue Oyster Cult, Dio-era Black Sabbath, pre-Halen Sammy Hagar, even Devo to give the right atmosphere to the bloody, spacey, sexy, funny, and stoned proceedings. And honestly, 35 years after I first saw it, it turns out I'm still here for it. Every minute of it. I loved it again and I suspect I always will, because sometimes I still, in the privacy of my own home where I can be no harm to anyone, want and need to be a teenage boy.