text: The term "heavy metal" can be a bit confusing because the meaning has changed over time and means different things to different people.\n\nOriginally, all metal up until about the mid 1980's was just called heavy metal. This included Iron Maiden, Judas Priest, Black Sabbath and some of the hard rock bands that influenced them like Led Zeppelin, Deep Purple, and Blue Oyster Cult.\n\nTo metalheads, heavy metal is a term that differentiates that certain type of metal from thrash metal, death metal, etc. Main characteristics of the heavy metal sub-genre are two-guitar harmonies, aggressive riffs, and powerful clean vocals with a lot of emphasis on the upper ranges. \n\nIt's really hard to classify the metal sub-genres because there is a lot of similarities and crossovers between the genres. You'd really have to listen to a lot of metal to truly understand all of the distinct characteristics of each one.