A metal head is a person who loves metal music. Some of them may dress a certain way, such as blue/black jeans and extremely often band shirts. They only wear band shirts of bands they love and are talented. After the 80's, metal went downhill and became a lot less common. Most play a musical instrument, ELECTRIC guitar, especially flying V's, as well as bass guitar, drums, etc.
Metal: Old Metallica, Iron Maiden, Slayer, Megadeth, Dragonforce, Children of Bodom, Pantera, Iced Earth, Dream Theater, Venom, Exodus, Death, Kreator, Black Sabbath & Ozzy, Motorhead, Testament, Judas Priest, Hammerfall, Sonata Arctica, Grim Reaper, etc.
NOT metal: Slipknot, Korn, Disturbed, etc.
You went to the Slayer concert? Holy crap, kick ass my fellow metal head.