Self-confessed in-it-for-life metaller Sam Dunn is narrator and guide in this erudite documentary about that most misunderstood and derided of musical genres, heavy metal. Dunn is an anthropologist and, as such, intends to challenge outsiders' perceptions about the clichés of satanism, spots and sexual confusion with an investigation of the realities inside the metal scene and its many sub-genres. Along the way he speaks to metallers of note Tony Iommi (Black Sabbath), Bruce Dickinson (Iron Maiden), Lemmy (Motorhead) and Alice Cooper plus representatives of the less mainstream sub genres. Particularly entertaining/enlightening are the slightly scary, mostly hilarious "Satanists" from the, frankly, nutty Scandinavian black metal scene. Dunn's anthropological intentions are often overshadowed by his own passion for the music he's studying and on the whole his movie is preaching to the converted but I dare say if you're interested enough to read this review, you're already in the choir.