Metallica was easily the best, most influential heavy metal band of the '80s, responsible for bringing the music back to earth. Instead of playing the usual rock star games of metal stars of the early '80s, the band looked and talked like they were from the street. Metallica expanded the limits of thrash, using speed and volume not for their own sake, but to enhance their intricately structured compositions. The release of 1983's Kill 'Em All marked the beginning of the legitimization of heavy metal's underground, bringing new complexity and depth to thrash metal. With each album, the band's playing and writing improved; James Hetfield developed a signature rhythm playing that matched his growl, while lead guitarist Kirk Hammett became one of the most copied guitarists in metal. Lars Ulrich's thunderous, yet complex, drumming clicked in perfectly with Cliff Burton's innovative bass playing.
After releasing their masterpiece Master of Puppets in 1986, tragedy struck the band when their tour bus crashed while traveling in Sweden, killing Burton. When the band decided to continue, Jason Newsted was chosen to replace Burton; two years later, the band released the conceptually ambitious ...And Justice for All, which hit the Top Ten without any radio play and very little support from MTV. But Metallica completely crossed over into the mainstream with 1991's Metallica, which found the band trading in their long compositions for more concise song structures; it resulted in a Number One album that sold over seven million copies in the U.S. alone. The band launched a long, long tour which kept them on the road for nearly two years. By the '90s, Metallica had changed the rules for all heavy metal bands; they were the leaders of the genre, respected not only by headbangers, but by mainstream record buyers and critics. No other heavy metal band has ever been able to pull off such a trick. 

However, the group lost some members of their core audience with their long-awaited follow-up to Metallica, 1996's Load. For Load, the band decided to move toward alternative rock in terms of image — they cut their hair and had their picture taken by Anton Corbijn. Although the album was a hit upon its summer release — entering the charts at number one and selling three million copies within two months — certain members of their audience complained about the shift in image, as well as the group's decision to headline the sixth Lollapalooza. Re-Load, which combined new material with songs left off of the Load record, appeared in 1997; despite poor reviews, it sold at a typically brisk pace through the next year. Garage Inc., a double-disc collection of B-sides, rarities, and newly recorded covers, followed in 1998. In 1999, Metallica continued their flood of product with S&M, documenting a live concert with the San Francisco Symphony; it debuted at number two, reconfirming their immense popularity. The band spent most of 2000 embroiled in controversy by spearheading a legal assault on Napster, a file-sharing service that allowed users to download music files from each other's computers; aggressively targeting copyright infringement of their own material, the band notoriously had over 300,000 users kicked off the service, creating a widespread debate over the availability of digital music that raged for most of the year. In January 2001, bassist Jason Newsted announced his amicable departure from the band.