Machine Gun Kelly, 31, got the crowd at his Indy 500 party performance to cheer even louder than they already were when his girlfriend Megan Fox, 35, joined him on stage at the Barstool Sports’ party at Grand Park in Westfield, Ind. for his song “I Think I’m Okay.” The actress walked out after the attendees were reportedly shouting her name for a while and looked gorgeous in a black crop top and fitted pants.