'I love you with all of me and am sending you all of the light and warmth I have to offer on this challenging day'.
The atrocity was one of a spate of terrorist attacks to hit Britain past year - the one in Manchester and four in London - that included bombings and deadly violence with vehicles and knives.
The performance will feature the Manchester Survivors Choir, a group of people who were in attendance on the night of the bombing, and Parrs Wood High School's Harmony Group, whose post-attack tribute went viral previous year and received praise from Grande herself.
They will attend the service at Manchester Cathedral alongside first responders, civic leaders and some of the scores injured in the suicide attack on May 22 previous year, which killed 22 people.
22 people were killed when a suicide bomber set off an explosive on May 22, 2017.
The attack came at the end of a concert by USA singer Ariana Grande who sent a message Tuesday to the people of Manchester.
Prince William the Duke of Cambridge and British Prime Minister Theresa May joined thousands of people who gathered in Manchester Tuesday on the first anniversary of a terror attack in the city which left 22 people dead. During Grande's July show in Buenos Aires, the singer reprised her take on "Somewhere Over the Rainbow", which she also performed at One Love. The fans were victims of a terrorist who detonated a bomb in the foyer of the venue as concertgoers filed out of the arena after Ariana's gig. Others left hand-written notes on Japanese maples that have been planted to form a "Trees of Hope" trail through the city.
Manchester’s mayor says the city is still recovering a year after concert blast
Paul Hodgson, stepfather of victim Olivia Campbell-Hardy, 15, said of the anniversary: "We're going to get through it with friends and family, the 22 families together".
The crowd also heard from some of those singing, including two members of the A City United Choir, a one-off coming together of the signing groups attached to the city's Premier League football teams.
Later Tuesday, more than 3,000 singers from local choirs will come together to mark the anniversary in Albert Square.
As images of the victims were displayed on screens, 22 candles burned on the altar, made using the wax from the thousands left at city centre memorials in their memory in the hours after the disaster.
William read a passage from the Bible's book of Corinthians, ending: "Faith, hope and love abide, these three; but the greatest of these is love". "It's a case of standing strong".
After performances by several choirs, the crowd joined in a mass sing-along of tunes including Grande's "One Last Time", "Look Back In Anger" by Oasis - an unofficial anthem of Manchester after the bombing - and The Beatles' "All You Need is Love". Instead 100 pedestrians and a handful of transport police who rushed to the scene improvised, with T-shirts for tourniquets and crush barriers for stretchers.
The congregation and the city observed a minute's silence at 2.30pm for the victims, a silence also observed by MPs in Westminster.