The official start of the three day trip takes place at Buckingham Palace later this morning.
The US president said he expected his three-day visit to be "very important" and "very interesting" as he left the White House on Sunday evening.
Protesters in London is expected to gather at Trafalgar Square and "follow Trump" to various locations including Whitehall.
The protest comes ahead of a controversial three-day visit by the president to the United Kingdom, which began with Trump intervening in the upcoming contest to replace Theresa May as prime minister.
Banners created by UK based human rights organization Amnesty International and unfurled over Vauxhall Bridge in central London on June 3, 2019 to coincide with the UK State Visit of US President Donald Trump.
The invitation by May was extended to Trump during her visit to the US on January 27, 2017, sparking criticism in the United Kingdom due to the president's controversial travel ban on seven Muslim-majority countries.
London Mayor Sadiq Khan, at the centre of a continuing feud with Trump, has said he was not invited to the event but that he wouldn't attend if he was. Both leaders gave short speeches before dinner began.
Trump could be seen chatting with members of the Guard of Honor as the rest of the American delegation, from a terrace, observed the elaborate arrival ceremony, complete with the playing of "The Star-Spangled Banner".
He briefly held hands with Melania as they walked to their helicopter, Marine One.
Ollie Nancarrow, 18, cut an image of a giant penis, a polar bear and a climate change message on his family's land close to Stansted Airport, Essex.
Trump kicked off the trip with a tweet blasting London Mayor Sadiq Khan, who says the American president should not get red-carpet treatment in Britain.
In May 2016, Trump challenged Mr Khan to an IQ test, after the Mayor said the President's views on Islam were "ignorant".
He then went on to insult Khan's height, while spelling his name wrong.
Mr. Trump also visited Westminster Abbey to lay a wreath at the Tomb of the Unknown Warrior and on Wednesday he will join the Queen and other dignitaries in Portsmouth for a ceremony commemorating the 75th anniversary of D-Day.
Donald Trump arrived for his state visit in the only way he knew how: noisily.
May announced her resignation last month after failing to get her Brexit deal through parliament and twice delaying Britain's European Union departure.
After arriving for his multiday state visit, Trump also complained that because Fox News was not available, he had to watch CNN.
With a 41-gun royal salute ringing out across the royal palace's lawn, Queen Elizabeth II and Prince Charles shook hands with the United States leader and First Lady Melania Trump before British soldiers played the national anthems of the two countries.
His first presidential visit to Ireland, which will include a stay at his coastal golf club.
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