The Excessively Hardcore Fan
This person has been a fan of the band since before everybody else in the world had ever heard of them, including any and all members of the band's immediate families. He still hasn't fully forgiven his former heroes for writing songs that people besides him enjoy but attempts to maintain his aura of superiority by memorizing every detail about the band's backstory, as well as the liner notes to all of their albums, songs, and Volkswagen commercials. He is typically found sitting quietly in the front row, angry at the more casual concertgoers for being too busy singing along, dancing or otherwise enjoying themselves to really appreciate the music. His new favorite band after this concert will be the "avant garde" opening act that nobody else liked.
The Guy who Just likes to Smoke Pot
This person knows next to nothing about the band performing, but he does know that smoking pot with other people at a concert is a lot less pathetic than smoking it alone in your parents' basement and watching a Bewitched marathon. Throughout the night, he will largely ignore anything the band is doing onstage and instead devote all of his energy to figuring out if people want to smoke now or wait until the headliner starts performing. Typically found at outdoor concerts on the open lawn area, after smoking, he will either spend the rest of the concert lying down in a state of drugged bliss or continually asking if anyone wants to skip out early and go hit up the nearest Denny's.
The Overgrown Hippie
This person is typically an aging baby boomer who remembers all too well how horribly his adolescence went after he found out his dad didn't share his undying love for Country Joe and the Fish. Right then and there, he made a vow that he wouldn't make the same mistake when he had kids. No, with Clapton as his witness, he would take more of an active role in learning about the music they listened to. And yes, that includes acompannying them to concerts, despite their insistence that this is unnecessary since they can just burn him a CD if he's really that interested. He is typically found surrounded by one to three teenagers, happy that he paid for their tickets but unhappy that he won't stop talking about how Modest Mouse is basically just a newer, less talented version of Jefferson Airplane.
The Guy Trying to Get Laid
This person is not at the concert to listen to music. He is at the concert because he knows that there are girls there who will either be intoxicated via alcohol or via the band's slow romantic hit. Coincidentally, this happens to be the one song this guy knows all the lyrics to, and he swears he could play the guitar part, too, if only he had remembered his acoustic. Not that it matters, though, because he'd be way too distracted by how beautiful your hair looks in the moonlight to focus on playing anyway. It's just that this song reminds him so much of the two of you, you know? Like, that lyric "in your eyes I see the doorway to a thousand churches" might as well be about two drunk people who just met at a concert, you know? And then there's the part aboutooh, right here, you sure? Nice.
The Wannabe Groupie
This person is, above all else, not a real groupie. The real groupies are hanging out backstage and have been with the band since Portland. However, due to a few minor daddy issues and too many viewings of Almost Famous, she has decided that being selected to be a groupie for the night would be a wondrous life-fulfilling experience, and she will do whatever it takes to make that happen. She is typically found towards the front of the concert, decked out in every type of clothing that exists with the band's logo on it and singing along violently to every song in an attempt to convince the band members that she is the only fan here worthy of giving one of them a blowjob. They will take all of this into account when making their careful final selection for the night, following which they will pick the girl with the biggest boobs.
The "Freebird" Guy
This person shouts out "Freebird!" at least once a concert, as he is unaware that this stopped being clever in 1977. He is usually a southerner and always a douchebag. That is all you need to know about him.
The Band Member
This person has made quite a lot of money recording songs that several million people like listening to and recently discovered that he can make even more money by having people pay to hear him perform these songs live at pre-established venues. Depending on who you ask, he is either a musical genius who is redefining his genre or a huge corporate sellout who is destroying music. He is typically found on an elevated platform enshrined in light in front of everyone else at the concert, shouting things such as "Hello [name of town]" to drive the crowd into a frenzy. He is also generally surrounded by three to five people of roughly the same level of fame and musical talent as himself.