3. Black Sabbath - 'Black Sabbath'
Black Sabbath's 1969 debut LP is the Big Bang of heavy metal. It's impossible to imagine how the genre would have evolved without it. At the time the music wasn't even called metal, and the four members of Black Sabbath had virtually no idea they were breaking ground. They did know they didn't like the hippie music of the day, and they wanted to create music that scared people in the way horror movies scared them. The disc was recorded in a single day at a London studio, and in stores just three months later. Much to their surprise, it found a huge audience. They didn't truly become superstars until their second album, though.