Brian Deegan co-founded Metal Mulisha with Larry Linkogle. He came out of Nebraska to race pro motocross and was riding for Moto XXX when he won the 125 main at the 1997 LA Supercross. He passed Robbie Reynard for the lead, held off Kevin Windham and ghost rode his bike across the finish line.

Deegan rode and filmed with the Mulisha crew through those early freestyle years. In 2003 he landed the Mulisha Twist at X Games. He had practiced it in a foam pit, but that was his first time landing it on dirt. He took bronze in Freestyle and gold in Best Trick that year.

He later moved into rallycross and short-course truck racing, winning X Games Rallycross gold in 2011 and Lucas Oil championships in both Pro Lite and Pro 2. He competed, filmed and toured with MM while building the company alongside Linkogle.