Go to some local metal shows, try out a bit of everything (just in a smaller scale) to see what you can and can't cope with, and then size it up.
I've been to numerous big gigs (Tool, Nine Inch Nails, Mastodon, Opeth, Enter Shikari, Paradise Lost, and more) and not had a problem at any. I go in pits, I'm pretty much always near the front, but I'm one of those people who dooesn't get claustrophobic and I don't freak out if I'm in the crush near the front, I just wait for a song to finish and then move back a bit to where there's more space if it's too cramped. But yeah, everyone's different y'know?
If you're gonna go to a Godsmack show, there WILL be pits, there WILL be crushes, there WILL be morons throwing their weight around. You get douchebags at any gig. Seeing as you can't really hear someone if they politely ask them to dick about, they just throw a punch instead. 90% of people at gigs are there to enjoy themselves, and the moron ALWAYS will get dealt with.
Also, if you go in a pit, 9 times out of 10, people obey the unwritten rules of the pit. If someone goes down, they pick 'em up, if someone doesn't wanna be in the pit anymore, you let em stand to the side and don't push em back in. Of course moshing is violent, but it's nothing personal, it's just a way of using that adrenaline the music gives you, if someone's getting hurt, then the people in the pit know its gone too far.
As much as metal crowds may seem scary, they're there to see the same band as you, and that means everyone in the venue is a friend.
Metal fans have the biggest sense of camraderie I've ever seen, metal crowds are some of the friendliest I've ever been a part of.
There's more to be worried about if you were seeing an indie band to be honest.
Sorry for the essay, but yeah, go, take earplugs, find a spot that suits you, move if it gets uncomfortable, and just don't fret, EVERYONE is there to enjoy themselves with their fellow fans of that band, so you enjoy it too.
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