It was written by Sullivan and Key Wane for her third studio album Reality Show (2015), while production was helmed by the latter.

[2] After 7 and Sullivan performed a mashup of "Let It Burn" and "Ready or Not" at the 2015 Soul Train Music Awards, celebrating fellow honoree Babyface.

[3] A throw-back to 1980s music,[4] the song is a dreamy, simmering late-night ballad,[4] that is built upon a synth-heavy instrumentation.

[5] Lyrically, "Let It Burn" was inspired by a previous relationship during which Sullivan felt that she was not acting like an ideal girlfriend.

[4] Pre-produced by frequent collaborator Wane, she initially recognized the melody of "Let It Burn" as something she had heard before, but was not aware of the sample until months after she recorded it.