In 2002, McMillan made his debut in the music industry with "Hope Anthology, Volume 1". Following this successful independent album, he released "The Song Inside: The Sounds of Breaking Down" in 2005, which featured the popular track "How He Loves". The song gained widespread recognition, and was covered by influential musicians in the Christian music scene, such as the David Crowder Band. In 2008, McMillan independently released his third album, "The Medicine", which was later re-released under the Integrity Music label in 2010, followed by "Economy" in 2011. In 2014, he partnered with Josh Lujan Loveless to create Lionhawk Records, which released "Borderland" after a successful Kickstarter campaign that nearly doubled the initial goal. The album debuted at No. 41 on the Billboard 200 chart and secured the No. 4 spot on Billboard's Top Christian Album chart. Subsequently, all of McMillan's studio albums were released through Lionhawk Records, including "Mercury & Lightning" in 2017 and his most recent album "Peopled with Dreams" released in 2020.