DESPITE its title, this is an impressively intelligent documentary from scholar and metal lover Sam Dunn.

He turns his academic eye to the whole culture of heavy metal.

There are graphs and charts showing how each sub-genre of metal fits into the grand scheme of things, but it's by no means a university lecture.

With a fan's enthusiasm, Dunn adds plenty of metal anthems plus interviews with heavy metal heavyweights to the mix. And whatever your leathered leaning, there's something to suit all tastes.

Highlights include why out-of-towners' are more likely to be metal heads, and Ronnie James Dio claiming his gran invented the devil horns.