Hundreds of anti-monarchy protesters have gathered in central London’s Trafalgar Square, just a mile away from Westminster Abbey where Charles will be crowned.

Their chants of "not my king" were met with boos from others in the crowd who are fans of the royals.

-ABC News' Ibtissem Guenfoud and Patrick Reevell

Charles’ coronation is the first since 1953, when his mother was crowned.

The queen’s coronation also took place at Westminster Abbey, where every coronation service has taken place since 1066.

Over 8,000 guests filled the abbey for Elizabeth's coronation, including Charles, who was 4 at the time.

One famous photo shows Charles resting his head on his hand as he stands between his grandmother, Queen Elizabeth The Queen Mother, and his aunt, Princess Margaret.

Wearing suits, fascinators, military uniforms and medals and religious clothing, guests began filing into Westminster Abbey Saturday over three hours before the start of Charles’ coronation service.

Actress Emma Thompson and singer Lionel Richie, who is performing at Sunday's coronation concert, are among the guests.

Watching the coronation service in-person are over 2,200 invited guests who represent over 200 countries, according to Buckingham Palace.

In addition to royal family members, the assembled guests include heads of state, members of foreign royal families, representatives from charities of which Charles and Camilla are patrons, faith leaders, Nobel Prize winners and members of the Diplomatic Corps.

Just as with royal weddings and funerals, Charles’ coronation is expected to be viewed by millions of people around the world.

Cameras are allowed inside Westminster Abbey, so everyone at home will get a chance to see the biggest moments of the day.

ABC News, "Good Morning America" and ABC News Live will have special coverage of the coronation on Saturday, May 6, from 5 to 10 a.m. ET.

The five hours of special coverage will also be available to stream on ABC News' digital platforms, including ABCNews.com and GoodMorningAmerica.com, mobile apps, social platforms and over-the-top (OTT) services.

ABC News Live will also immediately re-air the five hours of coverage from 10 a.m. to 3 p.m. ET on Saturday, May 6.

Charles and his wife Camilla were greeted with big cheers Sunday as they arrived at the coronation concert in Windsor, England.

The newly-crowned king and queen got a rousing three cheers from the crowd as they stood in the royal box.

Seated with Charles and Camilla are members of the royal family, including Prince William and Kate, the Princess of Wales, and their two oldest children.

Actor Hugh Bonneville, the concert's host, opened the show by recognizing Charles' "lifelong passion for the arts." Bonneville got a quick laugh from Charles when he referred to the king as "the artist formerly known as prince."