"Monster" was allegedly written by Michael Jackson, Eddie Cascio, and James Porte, with the rapping segment written by Curtis Jackson.^[2] Jackson allegedly recorded the songs in 2007 while he was living with the Cascio family in New Jersey. Other tracks recorded during that time include "Breaking News" and "Keep Your Head Up", as well as "All I Need", "All Right", "Everything's Just Fine", "Black Widow", "Burn Tonight", "Let Me Fall in Love", "Soldier Boy", "Ready 2 Win", "Stay" and "Water". 50 Cent did not record together with Jackson physically; after Jackson's death, he received a call to come into the studio and perform his portion of the track. Once in the studio, the rapper worked with producer Teddy Riley on the song.^[3]

On December 10, 2010, the song was officially released on the posthumous album Michael, and two original demo versions leaked online in 2015. Also, an alternative version that doesn't feature 50 Cent surfaced online before the album's official release.

"Monster" received mainly negative reviews from music critics. Huw Jones from Slant Magazine said "Monster" is "weighed down by an unnecessary rap by the increasingly unnecessary 50 Cent".^[4] Alexis Petridis from The Guardian said the song was "a lumpy attempt to re-create the atmosphere of Thriller's title track".^[5] Greg Kot from Chicago Tribune said the song picked up "an unfortunate theme in Jackson's latter-day work as the oppressed media victim".^[6]

The authenticity of "Monster" was questioned as soon as it was released.^[7] Doubts over whether the vocals were actually by Jackson have been raised, reportedly by Jackson's mother Katherine and his two eldest children,^[8] in addition to many of his fans.^[9] His brother Randy Jackson posted a series of messages about the album on his Twitter account stating that family members were not allowed at his studio where the album was being completed.^[10] According to Randy, when producer Teddy Riley played him some of the tracks, "I immediately said it wasn't his voice".^[10] In a statement, Sony Music Group countered that it had "complete confidence in the results of our extensive research, as well as the accounts of those who were in the studio with Michael, that the vocals on the new album are his own".^[11] Riley, Frank DiLeo and Jackson's estate have since defended Sony's claims that the song is authentic.^[12] Riley, who worked on the songs "Hollywood Tonight", "Monster" and "Breaking News", claimed that he had to do "more processing to the voice, which is why people were asking about the authenticity of his voice",^[13] stating, "With the Melodyne we actually move the stuff up which is the reason why some of the vibrato sounds a little off or processed, over-processed. We truly apologize for that happening, but you are still hearing the true Michael Jackson."^[13]

Many fans who have cast doubt on the Cascio tracks have suggested that singer Jason Malachi sang the lead vocals of the Cascio tracks, but a statement by the Jackson Estate said that he was not involved in the recording.^[12] On January 16, 2011, a statement appeared on Malachi's Facebook page noting he was the vocalist of the songs in question, calling it his "confession".^[14] He later claimed on Myspace that his Facebook and official website were hacked. Malachi's manager Thad Nauden later that day told TMZ that "someone created a phony Facebook page in Jason's name. Jason wants everyone to know beyond a shadow of a doubt, he did not sing a single note on the album."^[15]

On August 23, 2018, it was reported that Sony had admitted in court that the vocals on the three Cascio songs were not performed by Jackson and were instead recorded after his death by Malachi, apparently missing the first part of Sony's counsel sentence "[F]or purposes of the argument" which is used in court not to be an admission, but rather a statement of "even if the alleged action happened".^[16] However, the next day, Zia Modabber of Sony Music's law firm, Katten Muchin Rosenman, recanted these reports, stating that "no one has conceded that Michael Jackson did not sing on the songs".^[1]

On July 6, 2022, Jackson's estate and Sony Music removed the song, along with "Breaking News" and "Keep Your Head Up", from streaming services Spotify and Apple Music amid the allegations that the vocals are not Jackson's.^[17]

• "Monster" (alternative version without rap) – 5:19
• "Monster" (Jody den Broeder & Chris Cox club mix) – 7:32
• "Monster" (Jody den Broeder & Chris Cox dub mix) – 6:15
• "Monster" (Jody den Broeder & Chris Cox radio edit) – 3:49
• "Monster" (original demo) – 5:05

• List of unreleased songs recorded by Michael Jackson
• Death of Michael Jackson
• List of works published posthumously