Brendan McMillan's passion for music began at an early age. It was this passion that led him to get his first bass guitar at the age of 12. During his teenage years, Brendan spent his time playing with various bands in his hometown of Norwood, Ontario, Canada. At the age of 19, he decided to move to Toronto to pursue a career in music. He enrolled in the bass major program at Humber College School of Creative and Performing Arts where he studied Electric and Double Bass. It was during this time that his soon-to-be successful band, My Darkest Days, took its form. Hours and hours of jamming and writing music were put in, 7 days a week. After touring Ontario, Canada playing gig after gig for 4 years straight, all of the hard work began to pay off.

In 2009, My Darkest Days showcased for industry mogul L.A. Reid and in late 2009, the band signed to Mercury Records – Island Def Jam. Years 2010, 2011 and 2012 saw the band tour non-stop; playing shows all over North America, with a stint in The UK. While opening for acts such as Sick Puppies, Hinder, Papa Roach, Skillet, Buckcherry, Three Days Grace and playing many festivals, Brendan McMillan continued to write, record and produce music on the side. In 2012, My Darkest Days took part in a 5-month arena and amphitheater tour with Nickelback, Bush and Seether. "Pornstar Dancing", Brendan's first single, featuring Ludacris, Chad Kroeger and Zakk Wylde reached number one on the Active Rock Chart in late 2011 and is certified Platinum in Canada and certified Gold in the United States. The Band has two top ten rock albums and five top 40 charted singles on Active Rock. The band was also nominated for a Juno Award in 2011 for New Group of the Year.

Brendan is currently playing with Canadian sensation Andee (Universal Music Canada). They have played with major acts such as Bryan Adams, Third Eye Blind, Jessie J, One Republic, and Simple Plan.