Sure it's not the most in depth look at the Metal genre, but Sam Dunn did manage to cram a lot of stuff into a 90 minute documentary. The interviews with Mayham at Wacken and Gaahl from Gorgoroth are worth watching it alone. Also watching Dio take as many digs at Gene Simmons was quite entertaining as well. I'll post the two interviews just because they're that funny, but if you're a fan of metal than it's definitely something to check out.