'The Voice' Finale: Watch Ed Sheeran, Alicia Keys, Coldplay, BTS and More of the Night's Best Performances!

The singing competition's season 21 finale featured some star-studded performances!

The Voice's 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 Voice debut with a performance of his smash hit country crossover, "Fancy Like," and Matthew McConaughey and Nick Kroll were on hand to introduce their Sing 2 co-stars Keke Palmer and Tori Kelly performing a duet of “Christmas (Baby Please Come Home),” alongside The Voice's Top 13 artists!

Then, season 21 Mega Mentor Ed Sheeran returned to The Voice with a performance of his new single, "Shivers!" Unfortunately, a technical malfunction left Ed's mic muted for the first part of his performance, but, ever the consummate professional, he ad-libbed until things were back on track.

Following his semifinals performance of his new holiday hit, "You Deserve It All," John Legend took the stage with Carrie Underwood to perform their CMT-winning duet, "Hallelujah," off of her Christmas album, My Gift (Special Edition).

And, in addition to performances by Jennifer Lopez and Ariana Grande, a familiar "voice" returned during Tuesday's finale, as former coach Alicia Keys debuted a special performance of her new song, "Old Memories," from her new double album, KEYS (Original and Unlocked).

Ahead of the big finale, the coaches opened up to ET about Ariana's first season on The Voice. John praised her as a "conscientious and loving" coach, who offered her team members "specific and excellent advice." 

And while Ari was a bit down on herself for not having any competitors in the season 21 finale, Kelly Clarkson assured her that many coaches have been in the same position in Voice seasons past, while also praising her for putting an immediate emphasis on vocal health with her team. "I was like, how have we never talked about this! It's so important." Kelly remarked.

For her part, Ariana said she felt "so blessed" to have coached her first season of The Voice -- even if it didn't end in a victory.

"I wouldn't change anything about it. I know I'm out of the running in a big way, but I had the most beautiful time, and I feel like I got to do some really special work with these artists," she shared. "And I will continue to know and work with them, and I care deeply about them."

"I made incredible friendships, and learned so much from [my fellow coaches]," Ari added. "I'm so blessed to have been a part of it, and it was a very cherished experience to me."

See more from this season of The Voice in the video below.