From 2005 by the same guy that did the Rush documentary

Metal: A Headbanger's Journey is a 2005 documentary film directed by Sam Dunn with Scot McFadyen and Jessica Wise. The film follows 31-year-old Dunn, a Canadian anthropologist, who has been a heavy metal fan since the age of 12. Dunn sets out across the world to uncover the various opinions on heavy metal music, including its origins, culture, controversy, and the reasons it is loved by so many people. The film made its debut at the 2005 Toronto International Film Festival, and was released as a two-disc special edition DVD in the US on 19 September 2006.
You can stream it for free at

http://www.documentarymania.com/player.php?title=Metal