His family relocated to California in the early '80s, as Lars promptly put an ad in the local music paper looking for other similarly minded musicians looking to start up a band (even though the NWOBHM had yet to make an impression stateside). One of the first replies he received was from guitarist James Hetfield, as the pair agreed that they should form a band that was a reaction against the glam metal that had infiltrated Los Angeles at the time. Soon after, Metallica was officially born.
Several other bandmembers came and went, until a lineup consisting of bassist Cliff Burton, lead guitarist Dave Mustaine, plus Ulrich and Hetfield (the latter also doubling on vocals by this time) moved to San Francisco, building up a solid fan base due to their shows and a heavily circulated demo tape, No Life 'Til Leather. Metallica was offered a record contract with the independent label Megaforce if they agreed to move to New York, which they did, replacing Mustaine with Kirk Hammett in the process. Over the course of three releases, 1983's Kill 'Em All, 1984's Ride the Lightning (which was the group's first to be issued by a major label, Elektra), and 1986's Master of Puppets, Metallica became one of heavy metal's most promising new bands, until Burton's tragic death nearly derailed the group. With massive success just around the corner, the remaining members decided to carry on with replacement member Jason Newsted, resulting in such blockbuster releases as 1988's And Justice for All and 1991's self-titled release, which established the group as one of the biggest rock bands on the planet. The '90s saw more sold-out stadium tours and further hit albums (1996's Load, 1997's Reload, etc.), before Newsted exited the band in early 2001.
Between Metallica tours throughout the '90s, Ulrich kept himself busy forming his own record label, Music Company (via Elektra/Asylum) and jet setting with other rock stars as well as movie actors. In the late '90s, Ulrich received criticism from rock fans when he publicly spoke out against the mp3 file sharing internet server Napster, attempting to lend a hand in closing down the server by prohibiting Napster from including any Metallica songs - going as far as giving a list of Metallica fans who had downloaded songs of the group (which resulted in the ban of nearly 300,000 users from the service).