[2] "I'm in Love with a Monster" is a pop song that blends elements of R&B, soul, and hip hop with "jazzy" rhythms along with heavy and funky beats.

Its music video premiered at the Sony billboard in Times Square on August 27, 2015 and features the group dancing in front and inside a hotel with actors dressed as monsters, in reference to the song's addition in the movie.

[5] The song was released to digital retailers as a single, and was later featured on the Japanese deluxe edition of the group's debut studio album, Reflection.

An announcement of the artist involved in the track for Hotel Transylvania 2 was first made public by Lia Vollack, president of Worldwide Music for Sony Pictures Animation, on June 16, 2015.

[6] When making the announcement at the press release, Vollack commented that there were "few groups out there" that could match the "incredibly fun feel" and the "animated vision" that Genndy Tartakovsky brought to the movie and stated that Fifth Harmony "knocked it out of the park."

"I'm in Love with a Monster" was written by Harmony Samuels, Carmen Reece, Sarah Mancuso, Edgar Etienne and Ericka Coulter.

Carolyn Menyes from website "Music Times" commented that the song "takes on loving an unconventional type of guy, who is, well, a monster.

"[16] In a positive review, Joseph Earp of Renowned for Sound said that the song is a "testament" to the group's "myriad of skills" in which it does not feel like a "movie cash in".

[17] Writing for Fuse, Jeff Benjamin compared the "booming tuba" to the 1960s track, "Big Spender" and called the chorus "slick" and "repetitive".

[12] Phillip Picardi of Teen Vogue wrote that the song is "catchy and upbeat, with a nod to the '60s", from a cross between early Pussycat Dolls and The Supremes".

Each group then stands in a hallway, singing and moving to a camera before walking as Lauren holds a candle lantern in her hand as an ominous purple light beams in the background before turning blue.