"We love you so much, to the families we love you so much".
Grande, who described herself as "broken" following the May 22 bombing, had immediately returned to the U.S., interrupting her Dangerous Woman world tour and later promising to return for the charity concert.
"I want to thank so much for coming together and being so loving and strong, and unified".
Oasis' lead vocalist Liam Gallagher surprised the audience and sang the band's hit "Live Forever".
The season-11 finale of the show, created by Simon Cowell and featuring a panel of judges that includes Cowell and Amanda Holden, shouldn't distract from the concert and its "important cause", ITV said.
Donaldson 2 HRs, Blue Jays beat Yankees 7-5; Judge hits 18th
But New York (32-21) had set the tone much earlier, scoring two unearned runs after a rare Tulowitzki fielding error in the third. This was the fourth time the Yankees have hit four homers in an inning - they last did it on October 1, 2012, against Boston.
Emotions ran high as pair performed the song at the One Love Manchester concert, which was watched by millions. "Let no one take that away from you", she said.
Prior to the concert, Ariana Grande visited the Royal Manchester Children's Hospital, where many of her young fans are being treated after suffering injuries due to the terrorist attack.
Victoria is a 24-year-old singer who has written with and for Ariana Grande on several occasions, including for her Dangerous Woman album.
The gig, held in the wake of the Manchester attack on May 22, saw music stars from across the globe including Justin Bieber, Coldplay and Katy Perry take to the stage for a night of unity, healing and joy.
His eight-year-old daughter Hannah had left the Grande concert just before the deadly bombing and said she was "happy to be back" to see some of pop's biggest names. Texts cost £5 plus your standard network rate, with 100% of your donation going to the We Love Manchester fund.
All proceeds from the global distribution of TV rights will go towards the We Love Manchester Emergency Fund, set up by Manchester City Council in partnership with the British Red Cross.