Mr Burnham appeared on stage with representatives of political parties, religions and both of the city's football clubs.
Fellow fans Jasmine Mayers and Lydia Smith said they came to the concert "to show support to the victims' families".
Howard Donald and Gary Barlow of Take That perform during the One Love Manchester benefit concert for the victims of the Manchester Arena terror attack at Emirates Old Trafford, Manchester June 4, 2017.
Ariana Grande returned Sunday to Manchester to honor the lives of those lost there.
The 35,000 tickets put up for sale on Thursday at £40 each ($51, 46 euros) sold out in minutes with 14,200 free tickets set aside for those who attended Grande's May 22 concert.
He said: "What an fantastic thing we are doing tonight, would you not agree?"
Twenty-four children from a local school, some of whom were at the targeted Manchester Arena concert, will also join Grande on stage to perform her hit song "My Everything".
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Nearly two weeks after a terrorist attack outside her concert killed 22 and injured over 100 people, Ariana Grande has once again taken the stage in Manchester.
In between the two songs, he said: "I'm not going to let go of hope, I'm not going to let go of love, I'm not going to let go of god".
Singer Robbie Williams then took to the stage to lead the audience in a rousing rendition of his Manchester tribute song, "Strong". Campbell would have wanted to hear the hits, Grande said the teen's mom told her - and so the singer designed Sunday's concert to honor a pop fan's thirst for ebullience. The rapper had previously cancelled his scheduled performances at two music festivals in Washington D.C and Minnesota following the attack, and has been inseparable from Ariana in the two weeks since the attack.
"And just I was about to leave the room, Adam looked at me and he said, "hey Scooter, make sure you tell them don't go forward in anger, love spreads".
Bieber told the crowd, "You guys are so courageous...what an awesome thing we are doing tonight..."
"They demand our bravery, and I want to thank you once again for coming out here today and opening up our call that hatred will never win, fear will never divide us because on this day we all stood with Manchester".
"It's not easy to always choose love, especially in moments like these, it can be the most hard thing to do, but love conquers fear and love conquers hate. The most important responsibility we have in this time is to take care of one another". "I encourage you to choose love, even when it's hard".