After retiring from the US Army, Memphis-based vocalist Cullen Moore had dedicated himself entirely to pursuing a career in the music industry, officially forming Sleep Theory in 2019 as a studio project, blending his passion for hard rock, funk, and R&B. Sleep Theory's debut song, "Another Way," achieved an impressive milestone on social media in January 2023, reaching 500k views within just 36 hours of its release. Expanding into a four-piece band, Sleep Theory earned widespread acclaim on radio station SiriusXM's Octane program and captivating massive crowds during their initial live performances. By combining metalcore-inspired breakdowns, bluesy grooves, and a contemporary pop sensibility, they amassed an impressive 13 millions global streams in just six months. After signing a deal with Epitaph Records, their July single "Numb" debuted at number 34 on the U.S Top 40 Radio Mainstream Rock Song charts. The subsequent EP, Paper Hearts, generated 33 million strems in the next few months. Released in 2024, the single "Paralyzed" was followed with "Static" and "Ill", ahead of the debut album Afterglow, issued in May 2025.