On a scale of 1 to 10, Iron Maiden's heavy metal purity sits at about 100. Their galloping rhythms and classical fretwork as well as Bruce Dickinson's operatic pipes are all genre archetypes. Initially associated with the New Wave of British Heavy Metal, the group unloaded a slew of riveting albums, including 1983's infernal Piece of Mind, that injected the genre with heroic levels of speed and lyrics that descend into the depths of madness. Maiden have adopted more progressive elements as they've matured, while maintaining a scorching level of creativity and passion for sonic dread.