Genre Motif/Metal

Heavy metal really falls into two camps. Those who like the "power" aspect of it treat it as basically a "purification" of Rock's original ideals (before "those damn Brits ruined it all"), where it has the same general tone but a much harder edge than, say, The Rolling Stones. Often overlaps with the "hard rock" genre. Regular heavy metal and glam metal fall under this. But then you get into the "extreme" forms of metal, which tend more towards "darker" themes and more distorted sounds. The latter camp is especially popular in the portrayal of Darker and Edgier, where it is a popular genre for vampires, demons and other Ax Crazy character types to enjoy. It's tendency towards Heavy Mithril and growling vocals often make it the target of parody, though.

Examples:
 * Scrubs frequently has gags involving "speed metal". One episode had a delivery driver who likes "speed metal" (the song played is "Driving Down the Darkness" by Devil Driver, which is metalcore, or groove metal, depending on how picky you are) helps J.D. get to work. It then shows J.D. acting demon possessed while listening to it as the character riding with him tries to ignore it.
 * Metalocalypse basically has extreme metal as one of its core themes. Whether it's mocking the genre (with it's Gorn and over-the top fantasy/action bent) or paying a tribute to it (with songs that some viewers see as Crowning Music of Awesome) is rather up-in-the-air.
 * Brutal Legend is a tribute to the metal genre made into a Fantasy RTS/Brawler video game.