The band formed after drummer Lars Ulrich placed an advertisement in a newspaper saying that he was looking for musicians to play material consisting of Tygers of Pang Tang, Diamond Head, and Led Zeppelin with. James Hetfield, a guitar player who would become the lead singer of Metallica, answered the advertisement. Later, Lars and James would have contact from another young aspiring guitar player seeking a band, Dave Mustaine. Ulrich, Hetfield, Mustaine, and bass player Ron McGovney began playing in the band. Ulrich and Hetfield saw another bass player, Cliff Burton, playing at a concert, and asked him to join the band to replace McGovney, who was having trouble getting along with other band members. Burton later joined the band after Ulrich and Hetfield agreed to move from Los Angeles to San Francisco. In 1983, Mustaine was kicked out of the band for his drug and alcohol problems and violent behavior, and was replaced with guitar player Kirk Hammett who left his previous band, Exodus. Mustaine went on to form his own band Megadeth, who became extremely popular on the metal scene, and have become one of Metallica's metal contemporaries, along with Slayer and Anthrax. All four bands are collectively known as the Big 4 of thrash metal.