Here is the true defintion.

The most important fact about a metal head is a person who is dedicated to the music. Not just classic metal or thrash or death metal. Nu Metal is metal to. I listen to all kinds of music death metal, thrash metal, and even Nu Metal. You people who are saying that Korn or Limp Bizkit are not true metal bands are not true metal heads so much as closed minded people who are afraid of change.

Another important part of being a metal head is you have to be a loner and only hang out with other metal heads. They can often be aggressive from being isolated from the rest of the world. However, they're very friendly towards fellow metal heads. They are not always likely to win in a fight like some have said. Many are wimps from sitting inside and listening to music or playing their instruments all day.

Many metal heads have longer hair but it's not a necessity. Leather is also not necissary and I prefer to not have it. Some heads wear clothes that are a little darker (not goth but similar) but again, it's not necisarry.

Gestures include swinghead back and forth with the rhythm of music which has been mentioned. But you guys forgot one important gesture. Devils horns. Index finger and pinky extended into the air.

Metal heads also have to be rebels. They do whatever they want whenever they want but they are not always lawless. They are much less likely to kill people than a rapper.

A group of BAMFs (Bad Ass Mother Fuckers) that kick ass because they listen to and/or play metal, living the metal lifestyle. A metalhead's arch enemy is the EMO KID. Metalheads beat the shit out of emo kids on sight AT ALL TIMES.

metal heads are people that listen to the different kinds of metal and most of them hate emos but metal heads wear black band t-shirts and usually have long hair

Someone who listens to heavy-metal or death-metal music.

A metal fan.
People who call themselves Metalheads usually refuse to believe that anything besides their underground/old music is total shit and unbearable. Innovation is against the metal rules in their book. Of course not all metal heads are like this, but the one who try to stand out as hardasses are. If the band isn't "true" then it's shitty in their eyes. Nu-metal such as System of a Down, Slipknot, and Korn are too weak for them so they call everyone who listens to it "faggots". They usually categorize nu-metal listeners as faggots following the mainstream, yet they still listen to the same shit their "Metal head" dads listened to.

Some new metal is good, some black metal is good, some death metal is good, some of everything is good. Grow the fuck up.

Someone who thinks the fact that they enjoy metal makes them cool. When really after punk rock and then hardcore music became cliche, and played out, there needed to be a "scene" in place for douche bags to still be able to find each other. There's always emo, but unfortunately emo is fucking gay.

The true definition of a poser
Anyone who is any kind of dedicated listener to any type heavy metal crap music.