"It's not easy to always choose love, is it?" she asked. "Especially in moments like these, right? It can be the most difficult thing to do. But love conquers fear, and love conquers hate. And this love that you choose will give you strength. It's our greatest power."
Perry asked everyone watching – both at Manchester venue Old Trafford Cricket Ground and via television – to make a physical connection with someone next to them.
"So now as you stand here – all of you here – and all of you watching from wherever you are, standing next to a stranger or a family member or a friend or a loved one, let's just do this little exercise in love," she instructed. "Just touch the next person. Touch a person next to you. Make human contact. Tell them, 'I love you.' Look in their eyes. Say, 'I love you!' Do it. Everyone out there. Everyone at home. I encourage you to choose love even when it's difficult. Let no one take that away from you."
Perry performed her ballad "Part of Me" from 2010's Teenage Dream, and ramped up the energy for 2013 hit "Roar," strutting across the stage as the audience shouted along.
The all-star One Love Manchester, staged at the city's Old Trafford Cricket Ground, benefited the victims of the Manchester terror attack. Ariana Grande, Justin Bieber, Miley Cyrus, Coldplay, Liam Gallagher, Marcus Mumford and Pharrell Williams performed at the event, among others.
Liam Gallagher performed a poignant a capella version of Oasis' "Live Forever" during a show benefitting the victims of the Manchester terror attack. Watch here.