The recording artist released the song, featuring McEntire, Urban, Hillary Scott and Chris Tomlin, on his 30th birthday Monday.
Rhett said in an Instagram video that he hopes "Be a Light" encourages people to stay positive, especially amid the coronavirus outbreak.
"Really, the song is just about encouraging you guys to stay positive and to be a light in a dark time and a dark place," he said.
Proceeds from "Be a Light" will benefit the MusiCares COVID-19 Relief Fund, which supports people in need in the music community.
Rhett released his fourth studio album, Center Point Road, in May 2019. The album includes the singles "Look What God Gave Her," "Remember You Young" and "Beer Can't Fix."
Last week, Rhett rescheduled May and June dates on his Center Point Road tour due to the coronavirus outbreak. The tour was to begin May 28 in Gilford, N.H., and will now kick off July 15 in Charleston, S.C.
"Hey y'all, in effort to keep everyone safe & healthy during this time, we have proactively rescheduled our May & June dates on The Center Point Road Tour," Rhett wrote on Instagram. "I'm keeping you and your loved ones in my thoughts & prayers."
Rhett has three daughters, Willa Gray, 4, Ada James, 2, and Lennon Love, 1 month, with his wife, Lauren Akins. His father, singer-songwriter Rhett Akins, welcomed a baby boy with his wife, Sonya Akins, this month.