Wear an authentic concert tee or don't wear a band on your chest at all. Plain tees are fine, but wannabe tees have no place at a concert. If you have a souvenir tee from any metal concert, go ahead and wear it. If the only concert tee you own is from Air Supply, leave the authentic tee at home.
Put on your oldest, dingiest and most ripped up pair of jeans. They must be genuinely old and worn; not a new pair sporting the used look. Metal heads know the difference. Make sure your old jeans fit, or put on a beat-up leather belt (You don't want to lose your drawers in a mosh pit). If your old concert jeans are too small, find a secondhand store and locate a new old pair.
Choose motorcycle boots or a beat-up pair of tennis shoes. Don't wear open-toed shoes, slip-on loafers or high heels. If you wear cowboy boots, you are just asking for trouble.
Complete the outfit with gelled, wet-look hair and accessory pieces such as leather wrist bands or a studded dog collar. Women should wear heavy eye makeup. Dark, defined eyes are a must, but use waterproof products. You'll sweat at the concert, and you don't want the makeup to run.