The 24-year-old singer took to her Twitter account to mark the anniversary of the horrific incident, which saw a suicide bomber detonate a nail bomb outside the Manchester Arena just after her concert finished, and she admitted the milestone will be a "challenging" day.
"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", she wrote in a tweet that included a bee, the civic symbol of Manchester.
The Parrs Wood High School's Harmony Group joined several local organisations, including the Manchester Survivors Choir, which features Grande fans who attended the fateful concert a years ago.
Manchester is marking the day with a series of events including the memorial service at the cathedral and a musical tribute in the evening.
"The Manchester Arena attack showed the worst of humanity", said Ariana Grande as she spoke in detail for the first time about last year's bombing.
"Finally, we will stand together on the day of the anniversary, remember the victims and reaffirm our commitment to them and their families".
GETTYThe memorial service saw a lot of defiant voices speak up against terrorism
"We are showing Manchester and the world that we carry on", said Cath Day of the Manchester Survivors Choir.
A minute's silence - observed nationwide - was held at 2.30pm with tears inside the cathedral, where photographs of those killed were displayed on screens, and outside, where thousands watched in Cathedral Gardens.
With his wife and father looking on, he paid tribute to the "amazing work" of the emergency services and those who responded on the night.
"That's why I did my best to react the way I did", Grande said.
A larger single lit candle remembered bereaved families and friends, more than 800 who were injured, those who helped on the night and those who have helped with the recovery.
On the altar behind him were 22 candles - fashioned from the thousands left behind at the memorial in St Ann's Square past year - each representing one of the young victims. The Lord Mayor of Manchester, June Hitchen, and the Bishop of Manchester, the Right Reverend David Walker, were also part of the event.
The Oasis song, which was introduced via a video message by Noel Gallagher, became an anthem of defiance in the aftermath of the attack and was sung by a crowd in Manchester's St Ann's Square following a minute's silence on 25 May 2017.More news: 'I hear covfefe:' White House weighs in on Yanny vs. Laurel debate
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