Bates began his career in the 1990s scoring low-budget films like Tammy and the T-Rex, The Last Time I Committed Suicide, and Denial. His breakthrough into the mainstream arguably came in the early 2000s, when he worked on higher-profile projects like Get Carter, Half Past Dead, and Baadasssss! The 2004 remake of Dawn of the Dead was significant, as he would maintain long-term collaborations with its Director Zack Snyder, and Writer James Gunn.

Bates scored four of Director Rob Zombie's films, beginning with 2005's The Devil's Rejects. For Zombie's remake of Halloween and its subsequent sequel, Bates adapted John Carpenter's original themes and motifs in order to fit the darker, grittier, and more contemporary atmosphere of the films. It was around 2007 that Bates began working regularly on big-budget, blockbuster films; including 300, Doomsday, The Day the Earth Stood Still, Sucker Punch, and Conan the Barbarian. This did not, however, dissuade him from composing scores to smaller, independent films like The Way, Killer Joe, The Sacrament, and Flight 7500.

In 2014, Bates co-wrote and produced Marilyn Manson's record The Pale Emperor. The album debuted at number 8 on the Billboard 200, while the single "Deep Six" went on to chart higher than any other single by Marilyn Manson on Billboard's Mainstream Rock Chart. Bates joined the band in 2015 as the lead Guitarist for The Hell Not Hallelujah Tour. The album's song "Cupid Carries a Gun" was used as the opening title music of the TV show Salem, and Bates composed the show's score. In April 2015 he left Marilyn Manson to resume film work.

In October 2015, during a Q&A with Marilyn Manson at the Grammy Museum, Manson announced that he and Tyler were working on new music together again. In 2015 Loudwire listed 'The Mephistopheles Of Los Angeles' No. 1 best rock track & Rolling Stone included 'The Pale Emperor' in its Top 50 list of the best albums of 2015. He returned as the lead Guitarist during the tour with Slipknot in July 2016. In 2017, they once again joined forces in the studio for the follow-up Heaven Upside Down with a world tour kicking off July 20th, in Budapest, playing more than a 100 shows around the world. In January 2018, Tyler decided to return to his studio and work exclusively on film and television.

That same year, Bates composed the score to the stylish neo-noir action film John Wick, collaborating with Joel J. Richard and Marilyn Manson. The film proved a surprise critical and financial success, and Bates returned to score its 2017 sequel. He re-teamed with that film's co-director David Leitch to score a spiritual successor, the Cold War-era spy thriller Atomic Blonde.

Bates composed the Soundtrack for the PlayStation 3 games God of War: Ascension and Army of Two: The 40th Day, as well as the PlayStation 4 game Killzone Shadow Fall. Most recently he composed for the largest first-person shooter app in the world, China’s Crossfire.