season 21 finale is set to feature some star-studded performances!The star-studded live finale kicked off on Tuesday with a special performance from Coldplay and BTS! While the K-pop group wasn't able to take the stage in person, its members — RM, Jungkook, Jimin, Jin, Suga, J-Hope and V — joined Chris Martin and his bandmates via hologram as they performed their soaring collab.Next up, Walker Hayes made his debut with a performance of his smash hit country crossover, «Fancy Like,» and Matthew