Rhythm guitarist Bill Kelliher came up with an intro for this song off the cuff whilst hanging out in the studio's kitchenette when someone else was tracking. He recalled to Kerrang!: "I showed it to Brann (Dailor, drums/vocals) and he added his part, and suddenly it just came to life. It took the whole song to a different place."
"Lean On" was originally sent by Major Lazer to both Rihanna and Nicki Minaj's camps as a slower reggae track. After both parties rejected the tune, Major Lazer recruited Danish singer MØ to supply vocals and recorded it themselves.