In the late 1960s, a harder form of rock music called "heavy metal" was invented. The first use of the term was in a 1968 song by Steppenwolf, "Born to be Wild", and other early heavy metal bands appeared in the same year. Black Sabbath was the band that invented metal music in the late 1960s, the band played loud, hard rock music based on blues music. Heavy metal music was mostly based on the sounds of the electric guitar. The electric guitar in heavy metal is always amplified through powerful amplifiers so that it has a loud, distorted, angry sound. Other bands such Deep Purple, Black Sabbath, Judas Priest, Eric Burdon and Alice Cooper played even louder, harder forms of heavy metal rock music.