Sam Dunn, Chris Adler, Tom Araya, Gavin Baddeley, Blasphemer, Randy Blythe, Alice Cooper, Pamela Des Barres, Bruce Dickinson, Ronnie James Dio, Malcolm Dome, George Fisher, Tony Iommi, Joey Jordison, Lemmy Kilmister
The film discusses the traits and originators of some of metal's many subgenres, including the New Wave of British Heavy Metal, power metal, Nu metal, glam metal, thrash metal, black metal, and death metal. Dunn uses a family-tree-type flowchart to document some of the most popular metal subgenres. The film also explores various aspects of heavy metal culture.