Right as no one else here has said it yet. Long hair is metal. You can wear as many spikes, studs, band tshirts- whatever and you will never look metal. You will feel like an outsider at gigs, your real metal friends will be ashamed to be seen with you. It may well be shallow, fuck it, if you shave your hair off you will only be 50% metal. Don't do it. Short haired people will flame me- only because every single one of them wishes they have a proper metal 'do' but don't have the balls to commit to a look that confirms a definite lifestyle choice.
The only exceptions allowed are if you have pube hair (Messiah Marcolin), and if you're going bald (Kerry King).