This is an incomplete list of heavy metal festivals. Heavy metal (or simply metal) is a genre of rock music that developed in the late 1960s and early 1970s, largely in the United States and the United Kingdom. With roots in blues rock and psychedelic rock, the first heavy metal bands such as Led Zeppelin, Black Sabbath and Deep Purple attracted large audiences, and during the late 1960s and mid-1970s these band and others in their genre were featured at a number of historic rock festivals. Judas Priest helped spur the genre's evolution by discarding much of its blues influence.