Heavy Metal

Heavy metal (sometimes referred to simply as metal) is a genre of rock music that developed in the late 1960s and early 1970s. With roots in blues-rock and psychedelic rock, the bands that created heavy metal developed a thick, heavy, guitar-and-drums-centered sound, characterized by highly amplified distortion and fast guitar solos. The All Music Guide states that "of all rock & roll's myriad forms, heavy metal is the most extreme in terms of volume, machismo, and theatricality."
Heavy metal has long had a worldwide following of fans known as "metalheads" or "headbangers". Although early heavy metal bands such as Led Zeppelin, Black Sabbath, and Deep Purple attracted large audiences, they were often critically reviled at the time, a status common throughout the history of the genre. In the mid-1970s, Judas Priest helped spur the genre's evolution by discarding much of its blues influence; the New Wave of British Heavy Metal followed in a similar vein, fusing the music with a punk rock sensibility and an increasing emphasis on speed.
Heavy metal became broadly popular during the 1980s, when many now-widespread subgenres first evolved. Variations more aggressive and extreme than metal music of the past were mostly restricted to an underground audience; others, including glam metal and, to a lesser extent, thrash metal went on to mainstream commercial success. In recent years, styles such as nu metal have further expanded the definition of the genre. Link