Often confused with '80s hair metal (at least by American listeners), glam rock was an almost entirely British phenomenon that became wildly popular during the first half of the '70s. Glam rock was fairly simple, crunchy guitar rock put across with outrageous theatricality. Most of the music was unabashedly catchy, with melodies drawn from teenage bubblegum pop and hip-shaking rhythms from early rock & roll. But those innocent-sounding influences were belied by the delivery, which was all campy, glitzy showmanship and sexuality. In fact, one of the main reasons glam never caught on in the U.S. was that glam artists intentionally played around with gender conventions, dressing themselves up in outlandish, androgynous costumes and makeup. In general, glam rock fell into two schools.