King Charles III's coronation: The biggest moments of the historic event

Pop superstar Katy Perry took to the stage in front of Windsor Castle in a gold ballgown as she honored royalty.

In the audience, Charlotte, the youngest child of William and Kate, was spotted singing along as Perry opened with her hit song "Eye Of The Tiger (Hear Me Roar)," followed by another hit, "Firework."

Perry was also an invited guest at the coronation service Saturday for Charles.

She revealed onstage that she brought her mom to the coronation celebration and stayed in Windsor Castle.

William, the heir to the throne, honored his father with a speech recognizing Charles' decades of service to others and to the planet.

William was met by loud cheers when he took the stage in front of Windsor Castle.

He honored his father's service, noting the pledge of service Charles gave at Saturday's coronation as well as the "over 50 years of service" he devoted before becoming king.

"We're all so proud of you," William said.

The royal ended his speech by saying, "I commit myself to serve you all, king, country and Commonwealth. God Save the King."

Music star Lionel Richie performed his hit songs Sunday night in front of royalty.

Richie played the piano and sang his hit song "Easy (Like Sunday Morning)" in front of a crowd of thousands, including Charles, Camilla, William and Kate.

He then got up and danced as he sang another hit song, "All Night Long (All Night)."

In addition to performing at the coronation concert, Richie also attended Saturday's coronation service at Westminster Abbey.

Prince Louis, who stole the show at Saturday's coronation, is not in attendance at the Sunday night coronation concert at Windsor Castle.

William and Kate are attending the concert with their two oldest children, Prince George, 9, and Princess Charlotte, 8.

Louis has become a crowd favorite thanks to his lively personality at recent royal events, from last year's Platinum Jubilee to Saturday's coronation of his grandfather.