Last year, Machine Gun Kelly successfully reinvented himself, working with Travis Barker and going from B-list party-rapper to hyper-processed pop-punk star. The big change was weird, but MGK’s rock album Tickets To My Downfall is easily his biggest hit, and now he’s out here playing headlining sets at rock festivals. Last night, MGK closed out one of the big stages of Chicago’s Riot Fest. He happened to play at the same time as Slipknot, who were added to the festival a months before the show after Nine Inch Nails dropped out. And perhaps out of competitive spirit, MGK had some words for Slipknot during his set.