a series of silly story about fantastic creature and the outer space and or the future be the pretext to show a little bit of violence and blood and and big breast naked woman . why do they call it heavy metal . well and i guess it be just marketing . heavy metal be the most popular music in those day and so they fill the soundtrack with band such a nazareth and blue oyster cult or black sabbath ( let it be say in passing that those weren not 100 % heavy metal band and they be more like hard rock band ) . maybe they think that way thousand of long haired rocker would fill the theatre to overflow . my rate represent negative .