Thing is they never "sold out". I've listened to a lot of their songs, and they never just went mainstream. I never hear them on the radio, they aren't "that" mainstream. Well known among metal fans, yes, but that's about it. It's kind of like saying Pink floyd went mainstream. You're implying that you have to sell out to become mainstream. This is not true. And Pink Floyd are mainstream, I don't think you understand the concept of a mainstream band. I'm not talking about being mainstream to the general public i.e. pop bands. They are known among all metal fans, they are mainstream as far as the genre is concerned. Mainstream is like bands people listen to now only because everyone else is listening to them right? I don't see how Iron Maiden fits into there. At least at my school there aren't many people who know or listen to Iron Maiden. Pink Floyd though......a lot of people wear their like T-Shirts after maybe listening to one or two songs which really pises me off. A mainstream band is a band with a considerable amount of fans that makes a lot of people, people who care about the genre/s, know who they are. Iron Maiden are one of the most mainstream rock/metal bands out there.