Sombr brought out 5 Seconds of Summer during his Lollapalooza 2026 performance in Chicago on Thursday, July 30, for a full-throttle rendition of “She Looks So Perfect.” The surprise guest moment capped a set built around theatrical entrances, raw vocals, and enough swagger to fill the T-Mobile mainstage. Sombr teased the crowd before introducing the Australian band as “the greatest band in the fucking world.” Dressed in black with a lace shirt, feathered coat, and boa, Sombr later arrived from backstage in a car while holding a drink, then sprinted into the audience carrying a black flag painted with his name and the festival logo. Sombr Was Clearly in His Mainstage Era The stage design leaned into a New York street scene, complete with street signs and a construction sawhorse that suggested Sombr was still building his world in real time. The performance itself was already moving at full speed, with Sombr switching between gritty rock vocals and falsetto while covering the entire stage. Sombr also performed recent tracks including “My Body Isn’t Ready,” “Potential,” and “Homewrecker,” the last of which appeared on Rolling Stone’s list of the best songs of 2026 so far. The singer released his debut album, I Barely Knew Her , last August and has since made high-profile appearances at the Grammys and Coachella, where Billy Corgan joined him. Sombr’s next move is a North American tour this fall, ending with a hometown concert at New York’s Madison Square Garden on November 23. “Homewrecker” also features bass from former Prince collaborator Wendy Melvoin , adding another notable name to a breakout year that is getting increasingly difficult to ignore.