The "Havana" singer only allowed for "legendary behavior" during her visit as an advisor on the show.

The Battle Rounds officially began on Monday for season 21 of The Voice, and Camila Cabello stepped in to assist John Legend.

"Camila has all the experience she needs to be the perfect advisor for our team. She has navigated a singing competition before and done very well on it," Legend said in an interview with Extra TV. "She was part of a group, and in this battle setting, where the artists are dueting with each other, that's a very important skill to have. And obviously, she's an incredibly successful artist and performer in her own right, and all the things she's learned throughout these years are going to be so important for our team."

Cabello has had previous experience in television competitions. She rose to fame after the girl group Fifth Harmony was formed on The X Factor USA in 2012.

"I would not be where I am today if I hadn't auditioned for a show like this," Cabello said on The Voice. "It genuinely gives people an opportunity, which I think is so amazing, so beautiful."

The singer surprised jazz-soul stylist KJ Jennings and rocker Samuel Harness during the rehearsals for Team Legend's first pairing of the season as they prepared to perform Cabello's song "I Know What You Did Last Summer," which sparked her love with boyfriend Shawn Mendes.

"Shawn and I started writing this song in a dressing room at Taylor Swift's concert. But what's really interesting is for the session, we had Shawn and me in separate vocal booths, and we were just improvising at each other," she said. "And that is the bridge that you hear now. He and I were just kinds of bouncing off each other for that bridge part. Another fun fact is Shawn would never remember the words of this bridge, and I would always make fun of him because he always got the words wrong."

The chemistry between the singers on the competition reverberated through their performance after Cabello and Legend's coaching.

"The wild thing is Shawn and Camila wrote this song as their first collaboration before they were dating," Legend said after the battle performance. "And the way you all connected, um, like, the chemistry was great. They really enjoyed performing together. That's all I want to say — no pressure!" 

However, only Samuel got to stay on Legend's team.

The Voice is now playing on Mondays and Tuesdays on NBC.