Alongside the band's main lineup, the song features Jarrod Alexander and Jamie Muhoberac on drums and keyboard respectively.

It was later released to mainstream rock radio on May 17 through Warner Records, and the band debuted it live at the Eden Project that same day.

Alongside the main band lineup of lead singer Gerard, guitarists Ray Toro and Frank Iero, and bassist Mikey Way, the song features Jarrod Alexander on drums and Jamie Muhoberac on keyboard.

[17] It also incorporates elements of doom metal, basement punk, arena rock, post-metal, and metalcore;[18][19][20] The New York Times described the song as "prog-emo".

[15] The song opens up with static noise, before introducing a mellow electric guitar, piano, and a "laid-back drumbeat" paired with Gerard's distorted vocals.

[18] "The Foundations of Decay" then crescendos into the chorus, which Billboard described as a "full-blown head banger" with "anthemic force" in a similar vein to the band's 2006 single "Welcome to the Black Parade".

[13] Shutler believed that the song's composition combined elements from their past studio albums, viewing the "guitar breakdown" to be similar to one from The Black Parade.

[18] When discussing the group's beginnings, the song references the September 11 attacks by describing Gerard’s own experiences that day and what inspired him to found My Chemical Romance.

[18] At the end of the track, Gerard softly expresses his desire to continue doing nothing ("Yes, it comforts me much more" / "To lay in the foundations of decay") as the song begins to fade out, before he yells "get up, coward".

[21] When discussing the song's verse about the September 11 attacks, Cassie Whitt of Alternative Press viewed the lyrics to be similar to the hero's journey trope.

Whitt further wrote that the entire song could be interpreted as someone refusing to accept the call to adventure until a "supernatural force" intervenes, represented by the "get up, coward" lyric.

[24] Several writers complimented the song's lyrics and themes,[23][25] with Peters writing that it demonstrated My Chemical Romance's "epic storytelling".

[18] Jack Rodgers of Rock Sound described it as "six minutes of dark, destitute and dramatic story-telling and world-building" that was unlike anything the band had released up to that point.

[25] In their review of the band's live performance at the Barclays Center in September 2022, Danielle Chelosky of Alternative Press described "The Foundations of Decay" as a quintessential song in My Chemical Romance's discography.

[27][28] Suzy Exposito of The Los Angeles Times described the song as a "fist, bursting defiantly from the soil" towards people who thought that emo music had faded out of relevancy.

[28] NME said that it was My Chemical Romance's "fiery comeback" that "exceeded every current or ageing emo kid’s wildest dreams".