During her set, "Part of Me", singer Katy Perry told the crowd: "love conquers fear and love conquers hate, and this love you choose will give you strength and it's our greatest power", before asking the crowd to turn and hug the person next to them.
Some concertgoers clutched signs reading "For our angels" in tribute to the 22 people who were killed and dozens more injured when a suicide bomber set off a blast after Grande's concert at Manchester Arena on May 22.
Piers Morgan, who publicly slammed Ariana Grande after she jetted out to Florida immediately after the Manchester Arena attack on May 22, on Sunday apologised to the pop artiste and admitted that he misjudged her.
Grande rules the night, performing her own songs and then joining Coldplay to perform the song "Don't Look Back In Anger."That song, written by the Manchester band Oasis in 1995, has become a symbol of the city's resilience in the face of tragedy".
Miley Cyrus said she was "so honored to be at this incredible event" and performed "Happy" alongside Pharrell Williams, who also sang "Get Lucky".
The 50,000-strong crowd held a minute's silence in memory of those who have lost their lives in the last fortnight before the evening culminated with the stellar line-up on stage, singing a stirring rendition of Grande's hit One Last Time - before the 23-year-old broke down in tears as she sung Somewhere Over The Rainbow.
Marcus Mumford of Mumford and sons opened the show with "Timshel", followed by the Manchester pop group Take That.
"It's very important. We need to stand united against it now". The singers encouraged fans to raise a finger and create heart shapes with their hands to symbolise "One Love" to show the unity and strength of everyone there. "The only thing we'll feel here tonight is love, and positivity".
The Manchester concert comes the day after attackers targeted the heart of London, killing seven people.
Grande wore a white sweatshirt with "One Love Manchester" written on it.
Katy Perry, Justin Bieber, Usher, Miley Cyrus, Liam Gallagher, Niall Horan and The Black Eyed Peas were among other A-list acts to appear on stage, with the Old Trafford show raising money for the We Love Manchester Emergency Fund.