Thirty-something anthropologist Sam Dunn earned academic street cred with his thesis on Guatemalan refugees, and then set out to study the culture he truly loved -- that of headbanging heavy metal.

Dunn himself has been a headbanger since age 12, and he would have majored in metal studies at college if it had been in the curriculum. His documentary is a rock-solid examination of the culture of heavy metal. It opens with the definitive question: Who was the first metal band? He builds consensus on the best candidate, simultaneously paying tribute to the important influences that pre-dated the birth of metal.

Dunn explores all aspects of heavy-metal culture, from gender and sexuality to censorship to basic musical constructs of a heavy-metal song and band. The story of heavy metal is told via band interviews, concert footage, early fan home videos, fan interviews, festival experiences and even Senate hearings (the Parents Resource Music Center debacle in the 1980s).

Dunn interviews a veritable who's who of rock musicians and critics, including Chuck Klosterman, Dee Snider, Rob Zombie, Alice Cooper, Geddy Lee and Ronnie James Dio. The purchase price is justified alone by Dio's comment on his Italian grandmother's role in the genesis of the devil horns symbol. The DVD release includes a bonus documentary about the Norwegian black metal scene, filled with insightful commentary from the authors of Lords of Chaos.

Perhaps the most important legacy of Dunn's film is his Definitive Metal Family Tree, a masterpiece that traces metal sub-genres throughout the last four decades. Metal, Shock Rock, Hard Rock, Glam Metal, Stoner Metal, Thrash Metal, Black Metal, Grindcore, Grunge Metal, Industrial Metal, Hard Alternative and many more all have their place in Dunn's metal tree. It's an ironclad tree that features several hundred bands all in their proper places.