"Timebomb" was written by lead singer Nicholas Petricca, James Alan, and Oscar Holter; the latter also produced the track with Mike Crossey, who handled the production for most of the songs on Walk the Moon's third studio album, What If Nothing (2017).

Maiman recalled the band going into the studio to record some tunes and being excited when creating the track, saying: "We had this song that we wanted to put out so we just did it, you know?

[5] An extended play was later released on May 3, 2019, featuring the original and live version of "Timebomb", a remix done by Ryan Riback, and a producer's mix of the track.

[2] Writing for Rolling Stone, Patrick Doyle mentioned that the song is composed "of jagged synths and choppy guitars with a huge eighties throwback chorus in the vein of Jack Antonoff".

"[12] In an interview with Global News, Petricca stated that the lyrics for "Timebomb" are "about the fear of falling in love", mentioning that it is "a very scary [but] good thing".

Mitch Mosk, writing for Atwood Magazine, described the song as "an explosive shout-your-heart-out singalong full of the band's familiar pop passion".

[11] Billboard magazine's Angelica Acevedo said that it is an "upbeat track" that "depicts the all-too-common feeling of being wary about falling in love, but going at it full force anyway".

[14] Chris DeVille of Stereogum wrote that the track is "a perfectly OK entry into that neon-'80s-pop-as-filtered-through-Passion-Pit genre", but commented that "it doesn't have the same spark" as "Shut Up and Dance".

During the video, Petricca is seen dancing vigorously in several scenes, while drummer Sean Waugaman occasionally bashes a bright yellow drum set.

[24] On February 19, 2019, Walk the Moon performed "Timebomb" on The Tonight Show Starring Jimmy Fallon from a "minimal stage set up with cool-toned flashing lights".

[25] A video of the band performing a stripped down acoustic version of "Timebomb" in Vevo's white studio was uploaded to YouTube on May 9, 2019.