"You who were hurt or bereaved 12 months ago today are forever part of Manchester, forever part of us", said bishop of Manchester David Walker.
Twenty-three people including the attacker were killed in the terror attack at an Ariana Grande concert.
Pirate FM has held a minute's silence to remember those who lost their lives.
The American singer Grande, who visited the injured in hospital in the wake of the bombing and returned two weeks later to host a fund-raising concert, wrote on Twitter: "Thinking of you all today and every 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".
In May 2017, Grande had finished her concert at the Manchester Arena in the United Kingdom when a terrorist detonated a bomb, killing 22 people and injuring more than 500 others.
And DJ Nick Grimshaw also sent love to those affected by the attack, while also praising the One Love Manchester benefit concert, which was organised by Ariana and Scooter shortly after the attack.
Greater Manchester Mayor Andy Burnham said it was a day to "come together".
Prince William and Prime Minister Theresa May are among those attending a service of remembrance at Manchester Cathedral.
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The victims were represented by 22 lit candles on the altar, which were made using wax from the thousands left in their memory by mourners in St Ann's Square at the time of the attack.
A choir sang "Amazing Grace" and "Somewhere Over the Rainbow", and Christian, Jewish, Hindu, Sikh, Muslim and humanist leaders all addressed the congregation.
For the rest of the week, song lyrics will be projected onto St. Ann's Church, St. Ann's Square and New Cathedral street from dusk on May 22 through to May 26. "It's a case of standing strong".
"Music is supposed to be the safest thing in the world".
Wiganers joined in a national minute's silence to remember the 22 innocent victims of the Manchester Arena suicide bombing yesterday.
Bells will ring out across the city center at 10:31 p.m.to mark the exact moment of the explosion a year ago.
Police say 100 investigators are still working on the case.