More than 50,000 people have signed up to demonstrate in London, where they intend to fly an oversized balloon depicting the president as an angry baby in a diaper.
May's government has recently been shaken following at least three resignations of senior members of her cabinet - including Foreign Secretary Boris Johnson and Brexit Minister David Davis, following disagreements on how to exit the EU.
Trump "has proudly sparked passionate often divisive emotions about things, I think Americans living here to eager to turn out and express their views", he said. "With a lot of resignations", Trump told a news conference at the North Atlantic Treaty Organisation summit in Brussels. "I was happy when Obama did it".
"When we leave the European Union we will begin to chart a new course for Britain in the world and our global alliances will be stronger than ever", May said ahead of Trump's visit.More news: Harry, Meghan mobbed by fans on first official visit to Ireland
But the red carpet treatment is likely to be overshadowed by massive protests planned by Britons opposed to Trump's presence.
The US president is set to touch down for his visit on Thursday after sparking a new firestorm on the worldwide stage.
"I would be happy to see Hillary Clinton if she was president visit the UK".
London Mayor Sadiq Khan, a frequent Trump critic, gave his approval for the balloon to be floated, with a spokesperson saying last week that the mayor "supports the right to peaceful protest and understand that this can take many different forms". "Everywhere he goes there are protests, so I don't think it really makes a big impression on him".
A campaign is also underway to get "American Idiot", a 2004 song by the US punk rock band Green Day, to the top of the UK Singles Chart.More news: Polish Historian/Scientist Continues Interview As Cat Climbs On His Head
After a dinner for business leaders in Blenheim Palace, birthplace of Winston Churchill, he will spent the night in the ambassador's residence in north London.
From there, Trump and his wife Melania are expected to travel to Windsor to meet Queen Elizabeth.
Trump and his wife, First Lady Melania, will land at London's Stanstead airport after attending a North Atlantic Treaty Organisation summit in Brussels.
Along with trade and security links, Downing Street said key areas to be discussed between the two leaders included Russia, Brexit and the Middle East.
May welcomed the summit and said it could help address "malign activity" by Russia which Britain blames for a nerve agent attack in March on a former Russian double agent and his daughter in southwest England in March.More news: Teenage Girl Arrested for Posting Dance Videos on Instagram