Originally titled, "Monster Under My Bed" was written by Bebe Rexha and intended to be used on her own debut album. The chorus was later used for "The Monster".
Upon release the song was met with positive reviews from music critics, who compared the song to "Love the Way You Lie" (Eminem and Rihanna song). "The Monster" has successfully charted worldwide, topping the charts in twelve countries including Australia, Canada, France, Ireland, New Zealand, Switzerland, the United Kingdom and the United States' Billboard Hot 100. It also marks Eminem's first number one on the US Hot R&B/Hip-Hop Songs chart and has reached the top ten in Austria, Belgium, Italy and Spain.
In November 2012, Bebe Rexha was at Stadium Red studio in Harlem, New York working on a material to be included in her debut album. During the sessions Rexha stated that she "was in a really dark place, a dark head space. Figuring out where you are in life and trying to make shit work for yourself—it gets to you. You get super down on yourself. I was just trying to get out of a depressed phase." At that moment, she wrote the hook for "The Monster"; in the moment she wrote it she knew that it was going to be a song performed by Eminem. The singer further stated that she got the inspiration from the quote "about the monsters that are around us and that live inside of us"; additionally, Rexha was disappointed at being dropped from the Island Def Jam (record label).
The Senior Director of A&R for Shady Records, Riggs Morales started looking for potential songs to be included on Eminem's eighth studio album. When the producer of "The Monster", Frequency played the song for Morales he "freaked out" and asked for the verses to be stripped and ProTools sessions to be sent to Eminem. When Eminem heard the demo he then added his own verses and adjusted the instrumental portion(s) of the track. However, he left the background vocals sung by Bebe Rexha and choose Rihanna instead.