He rose to fame in 2018 following the release of his single "Murder on My Mind", a trap song that explores homicidal ideation.

As his mainstream breakthrough, its release garnered him further attention after he was charged with the double-murder of two fellow rappers in the "YNW" collective the following year, resulting in an ongoing legal battle and incarceration.

Prior, "Murder on My Mind" peaked at number 14 on the Billboard Hot 100 and led him to sign with 300 Entertainment to issue the song as a single for his debut commercial mixtape I Am You (2018), which was met with positive critical reception along with its follow-up, We All Shine (2019).

Both mixtapes entered the Billboard 200 chart and received gold certifications by the Recording Industry Association of America (RIAA); We All Shine contained the double platinum-certified song "Mixed Personalities" (featuring Kanye West), and his incarceration began shortly after its release.

His first two studio albums, Melly vs. Melvin (2019) Just a Matter of Slime (2021), both maintained his commercial success despite mixed critical response.

[3] In February 2019, he was arrested and charged with two counts of premeditated murder for which he faces life without the possibility of parole or the death penalty if convicted.

His first trial ended in a hung jury,[8] and as of January 2024, his retrial is paused and awaiting adjudication for the inclusion of digital evidence.

During 2018 he met and bonded with the Chicago rapper King Von, with whom he shared the same music manager, Jameson “100K” Francois.

[22] A music video directed by Cole Bennett with Lyrical Lemonade for "Mixed Personalities" featuring West was released with the album.

YNW Melly has been noted for his melodic vocals and his "mix of bright harmonies slathered in grit and soulful love-sick ballads".

[38] He announced on his Instagram:[39] "No I did not get locked up in Washington, but I am turning myself in today... a couple months ago I lost my two brothers by violence and now the system want to find justice.. unfortunately a lot of rumors and lies are being said but no worries god is with me and my brother @ynw.bortlen and we want y'all to remember it's a ynw Family I love you"On February 22, 2019, Complex reported that Demons and Henry were suspects in the fatal 2017 shooting of off-duty Indian River County Sheriff's Department deputy Garry Chambliss in Gifford.

[42][43][44][45] However, on November 9, 2022, the decision was overruled by an appellate judge, once again making Demons eligible for capital punishment if sentenced.

Surveillance footage showed him taking the seat inside the car from which experts determined the shots were fired.

Demons alleged the victims died as a result of a drive-by, even though prosecution evidence showed the fatal shots that killed the pair had come from inside the car.

[55] On September 22, 2023 Broward Circuit Judge John Murphy declined to grant the rapper bond as he awaits his a new trial set for October 2, 2023.

[57][58] In January 2024 the trial was put on hold indefinitely after a judge's ruling to suppress a promotional video about Melly's life from evidence prompted prosecutors to file an appeal.