The heir to the British throne also honored first responders to the attack on an Ariana Grande concert in May.
Like the Bataclan and Manchester Arena, Borough Market was targeted for being a place of celebration and joy.
The U.K. Home Office told British media that an investigation into foreign sources of funding for local radical Islamist groups is "very sensitive."
Katy Perry, Miley Cyrus, Pharrell, Take That, Usher and Niall Horan will also perform at the concert, which will benefit the Manchester Emergency Fund.
The pop singer and actress says she plans to return to Manchester for a benefit concert that will raise money for the victims and their families.
Hashem Abedi, 20, was arrested with his father, Ramadan Wednesday in the Libyan capital of Tripoli.
"The worst of humanity was on display in Manchester last night."
On Manchester's Curry Mile and in its mosques, people are wondering how terror came to their city.
Manchester police said they have made three additional arrests in connection to the bombing that killed 22 people.
Abedi blew himself up with an improvised explosive device, killing 22 after an Ariana Grande concert.
"it just doesn't feel real." Hundreds gathered for a vigil to remember the 22 victims of Monday's attack.
More than 22 people died after a violent attack at a concert in Manchester, U.K. on Monday.
More than a dozen victims had been identified in the press as of Wednesday afternoon.