Metalhead is a person who listens to metal music, no matter what subgenre of it.
A metalhead belongs to a subcluture which consists of metal music, dressing up metal like studs, spikes, leather or black clothes & band shirts in general. They often attend countless metal shows with all their metal buddies. Nothing wrong with it.
But metalheads divide in two, one side has the intelligent and the other the stupid. The first side usually had good grades at school, they never abused alcohol and are generally very educated, smart and intelligent people who just happen to like heavier music.
The other side however has people who nearly dropped out of school, drink alcohol more than anything else, swear, are violent and lack of brains.
Often these two sides of one subculture clash with eachother, making metal subcluture one of the most notorious and controversial of them all.
Metalheads also tend to be elitist towards the music they don't listen, EVEN inside their own subculture. check example 1
Not all metal listeners are metalheads. They do enjoy heavier music to a great extent, but they choose not to dress according the subculture
and are very open to all music. They do attend metal shows, but every gig that comes to the country isn't a metal
must. Those people aren't metalheads, they're metal listeners. check example 2
Metalhead 1: black metal is the ultimate grim, all melodic shit is gay!
Metalhead 2: I don't get black metal, it doesn't have any melody, it's just noise!
Metalhead 3: Shut the fuck up you two, both are just fine!
Metalhead 1&2: No YOU shut up, there's only ONE true metal genre!
Mary listens to the most evil metal music there is, but has only attended three shows in her entire life. She also loves to wear pretty high heels and lots of white (or any color that isn't black). She doesn't have many metalhead friends, she'd rather go shopping for new purses while listening Gorgoroth via her headphones. She's not a metalhead but metal listener.