Band founders Hannah "Han" Mee and Jim Shaw had met via Tinder and dated for four years, ultimately remaining close friends and housemates.

[2][1][7] One night in January 2018, while grieving a friend who had passed, the pair wrote their first song together, "Take Your Jacket", in 25 minutes on acoustic guitar while drunk off a bottle of wine.

[2][7][3][4][6] After writing several more songs, Mee and Shaw anonymously sent the demos to contacts in the industry and, after getting positive feedback, secured management and recruited bassist Tom Paton and drummer Harry Deller, whom they knew from the local scene.

[11] Both singles received BBC Radio 1 play on programs like Daniel P. Carter's Rock Show, Phil Taggart's Hype Chart, and Annie Mac's Future Sounds, as well as on Kerrang!

[29] With touring suspended due to the COVID-19 pandemic, Hot Milk performed at the virtual Five4Five Festival, alongside Deaf Havana, Don Broco, As It Is, Enter Shikari, Fatherson, The Dangerous Summer, and Tigress; the event raised money for NHS Charities Together.

[1][32][33] The first half of 2021 saw Hot Milk return to Reading and Leeds (sharing a date with Queens of the Stone Age, Yungblud, Neck Deep, Girl in Red, Ivorian Doll, 100 gecs, and Sofi Tukker)[34] and Download Festival (sharing a date with Frank Carter and the Rattlesnakes, Neck Deep, Boston Manor, Sleep Token, Holding Absence, and Malevolence).

[35] In June, it was announced Hot Milk had signed to British indie label Music For Nations, who would be releasing the band's second EP, I Just Wanna Know What Happens When I'm Dead, in September.

[45][46] In March, the band announced a third EP for Music For Nations, entitled The King and Queen of Gasoline, and released the lead single "Bad Influence".

[54][55][49] They returned to Slam Dunk Festival in June, headlined by Alexisonfire and Rancid and alongside The Used, The Wonder Years, Motion City Soundtrack, and Meet Me at the Altar.

In the following months, the band joined Blackbear's Nothing Matters Tour alongside Waterparks, State Champs, Mod Sun, and Heart Attack Man.

[71] In February 2023, Hot Milk headlined a pair of shows entitled "England's Screaming" at London's KOKO and Manchester's The O2 Ritz, where they were accompanied by As December Falls, Jools, and Clarence.

[16][17] Their music in this era drew comparisons to Tonight Alive, All Time Low, Forever the Sickest Kids, The Summer Set, The 1975, Metro Station, and Teenage Dream-era Katy Perry,[13][23][26][17] and was described as "genre-fluid",[2] "neon bright and loaded with calorific hooks",[2] and "infectiously fizzy".

[92] By their second EP, however, they had begun incorporating darker and heavier sounds,[84][87][32] drawing from alternative rock,[84] post-hardcore,[40] hip-hop,[28] drum and bass, and screamo,[1] and were compared to acts like Stand Atlantic, As It Is, Pvris, KennyHoopla, Yungblud, Blink-182, and Trash Boat.

[11][7][1][91][9][6] She[note 2] has also cited Beach Boys, The Prodigy, My Chemical Romance, MGMT, Taking Back Sunday, and genres like jazz, indie-electro, house, and the Haçienda era of drum and bass as musical inspirations.

[11][7][91][98] The band have also taken inspiration from Billie Eilish, Halsey, Bring Me the Horizon, Linkin Park, Twenty One Pilots, Andy C, Bicep, Oasis, Descendents, Queen, Metallica, Black Sabbath, and Madonna.

[2][27][38][91][9] Additionally, as early as the release of "Candy Coated Lies",[2] the band has often lyrically addressed social and political issues including capitalism, LGBT rights, gun violence, and climate crisis.