Metallica is a thrash/heavy metal band formed in Los Angeles, California, in 1981 by drummer and former tennis prodigy Lars Ulrich and guitarist and vocalist James Hetfield. They met after Ulrich placed a classified advertisement in the American publication The Recycler. Bassist Ron McGovney was an original member, and the band used several transient guitar players in their beginning stages, one of these were Lloyd Grant.

Metallica got their band name, when Ulrich was helping San Francisco area metal promoter Ron Quintana pick out a name for a new magazine to promote metal and the New Wave Of British Heavy Metal bands. Quintana came up with two suggestions: "Metallica" and "Metal Mania." Ulrich suggested that the name Metallica was lame and told him to use Metal Mania. Lars then decided to use Metallica as the name for the band he had just started.

In early 1982, Metallica recorded Hit the Lights for the first Metal Massacre compilation. Guitarist Lloyd Grant was brought in to do the solos on the track but was never a full member of the band. Desperate for a full time lead guitarist, Ulrich posted an ad in the local newspapers. Dave Mustaine from Huntington Beach, California, a guitarist from the band 'Panic' (later the lead singer of Megadeth) responded, and upon arrival started a sound check. Ulrich and Hetfield were so impressed with Mustaine's warm up and equipment that they asked him to join before actually auditioning. A few months later the band recorded a full demo, "No Life 'Till Leather", which quickly drew attention on the underground tape trading circuit. Conflicts with Mustaine eventually caused McGovney to leave the band, and he was replaced by Cliff Burton from Castro Valley, California, lured from his band Trauma in exchange for the other members of Metallica relocating to the San Francisco area.

Upon arriving in El Cerrito, California, the group quickly built a healthy local following in the Bay Area Thrash Scene via word-of-mouth and live performances. Metallica then traveled to New York in 1983 at the urging of local promoters Jon and Marsha Zazula, and after a few gigs the band signed with the Zazulas' brand new label, Megaforce Records. Shortly after arriving in New York, Mustaine was fired due to various disruptive, unproductive behaviors all related to alcoholism and other addictions. Kirk Hammett was drafted from Exodus to replace him. A pupil of Joe Satriani, Hammett brought to the band a more melodic and progressive guitar style quite different from Mustaine's.

After Hammett joined the band, the classic Metallica line-up was installed; Kirk Hammett on guitar, Lars Ulrich on drums, James Hetfield on guitar and vocals, and finally Cliff Burton on bass. Many saw Metallica's formation as a direct reaction to the prevalent rock and roll music of the early 1980s. Inspired by bands such as Motörhead, Diamond Head (declaring in the sleeve notes of 1998's Garage Inc. that "two heads were better than one"), Saxon and other bands of the New Wave of British Heavy Metal, as well as from hardcore punk bands like Misfits and Discharge. Yet Metallica's fusion of these influences transcended mere stylistic mash-up, creating a heavy, hard, dynamic, yet capably melodic style perfectly reinforced by the evolving depth of their subjects, lyrics and composition, most noticeably starting with "Ride the Lightning", which also was the first album to feature Hammett's songwriting.

Metallica's first album, Kill 'em All, was released in 1983 on Megaforce Records. The album set the template that they would follow throughout the 1980s, prominently featuring the heavy vocals and aggressive rhythm guitar of. "Kill 'Em All" did not have huge sales after its initial release, but it did establish Metallica a loyal fan following in the growing 'underground metal' scene.

In 1984 Metallica released their second album for Megaforce, Ride the Lightning. The new album expanded their form with longer songs that featured lyrical and instrumental growth that rose above some of the playing on "Kill 'Em All". One significant development on "Ride the Lightning", the song Fade to Black, presented a slower, more introspective lyric, musing on the perspective of someone contemplating suicide. Indeed "Fade to Black" represents the first such song in a tradition that would come to include Welcome Home (Sanitarium) (LP Version) and One. The inclusion of songs with these slower, more ballad-like passages and psychologically sensitive lyrics demonstrates one of the important factors that distinguished Metallica from most other thrash metal bands such as Anthrax, Slayer, and Megadeth, whose musical ability rivaled Metallica, but whose artistry never quite matched.

This development as songwriters continued with Master of Puppets, which many consider Metallica's finest album. It also featured the compositional influence of Burton more than any other Metallica album. "Master of Puppets" was to be the last record with Cliff Burton, who tragically died in a tour bus accident on September 27, 1986, in Ljungby Municipality, near Dörarp rural Sweden.
Later, Jason Newsted joined the band as a new bassist. He stayed in the band for 15 years and has released 5 Albums with Metallica (...And Justice for All, Metallica _{(The Black Album)}, Load, Reload and Garage Inc.) and appeared on the official Metallica Concert DVDs entitled Live Shit: Binge and Purge, Cunning Stunts and S&M.

In the Year 2000, there were some arguments between Hetfield and Newsted. This was basically because Metallica did not listen to Newsted's musical ideas and him only being credited for 3 songs on the above mentioned albums. Newsted then left the Band in 2001 and helped a fairly unknown band called EchoBrain to release their album. Once they successfully released it he left and joined Ozzy Osbourne's band. Newsted is now a member of Tommy Lee's band, Rock Star Supernova.

When Metallica released St. Anger in 2003, it received mixed reactions from fans and critics, but hit #1 on the Billboard 200 in its first week, after which sales plummeted and it became Metallica's poorest overall seller to date. While producing, the band searched for a new bassist. His name was: Robert Trujillo.

In January 2005 "Metallica: Some Kind Of Monster" was released. It is a behind the scene documentary filmed during the recording of the album St. Anger containing interviews with the band and former bandmembers.

As of May 2007, using Rick Rubin's critically acclaimed producing abilities, Metallica is recording a new album, which is as of yet untitled. It has an expected release in early 2008. Rumors tell that a world tour will follow the release and that Metallica will include a recording of 'The Ecstasy Of Gold' (a song from the film The Good The Bad & The Ugly) to start the album, as they have opened live shows with this track for years - most notably on S&M, with the San Fransisco Symphony Orchestra (conducted by Michael Kamen).