A person who only listens to metal and feels passionate that this is the best genre of music. They dislike other forms of music because of the simplicity of the instruments, bad singing, or just plain fail.
Normal music fan: You should really like the Jonas Brothers, Lady Gaga, or American Idol. Death metal is scary...only metal snobs listen to it.
Metalhead: Listen to music with real instrumentals. That's only metal music of course. Most other music isn't even as talented and will never come close.
A form of alternative rock music which pretends to be metal music due to some metal influenced riffs. This genre is considered to be metal for people who can't handle anything heavier than Breaking Benjamin.
Person 1: I was listening to some Breaking Benjamin. Are they metal or rock?
Metalhead: They are alternative metal music. They are too wimpy to play real metal, so they play alternative rock pretending to be metal.