"I'd like to wrap my arms around each and every one of you and tell you thank you from the bottom of our hearts," she told the crowd. "I am so honored to be at this incredible event surrounded by all you amazing people."
She continued, "For me, the most important responsibility we have on this entire planet is to take care of one another, and look what we're doing today and how amazing that is."
Stars such as Robbie Williams, Niall Horan, Pharrell Williams, Take That, and, of course, Ariana Grande, whose concert was the target of the May attack, also performed at the benefit show. Proceeds from the concert will go to the Red Cross' We Love Manchester emergency fund.
A terrorist detonated a suicide bomb at Manchester Arena last month, killing 22 others, including children, and injuring more than 100 people.
The show went on as about 160 miles to the south, Londoners reeled from a Saturday night terrorist attack that killed seven people and injured dozens more.