I just finished watching the documentary "Metal: A Headbanger's
Journey," and I totally recommend it.  I'm not a huge
metalhead;  I often find myself wearing flannel and praising the
90s.  Yet, some part of me has a serious love/hate thing going on
with metal, and the first album i ever bought was "...And Justice For
All" (at the tender age of 10!)

Anyway, this
documentary is worth it alone for the interview with the incredibly
well-spoken Rob Zombie, and the reasonable well-spoken Slipknot
(they're still wearing their masks).  He also isn't afraid to dive
into the many subgenres, like Norwegian Black Metal.  The
following exchange occurs with a member of Gorgoroth:

"What would you say is your primary influence"

15 seconds pass...

(entirely straighfaced) "...Satan."