While eyes will be on Mr Trump to see if he breaches any royal protocols, it’s also worth watching out for the Queen’s choice of jewellery.
Last year when the US president visited the UK, he and Melania had tea with the monarch at Windsor Castle.
It was thought that Her Majesty was sending subliminal messages through her choice of brooches during the three days that Mr Trump was in the country last year.
While the Queen has always remained neutral on political matters, people on Twitter couldn’t help but read into what her jewellery may - or may not - say.
Political commentator and journalist Daisy McAndrew tells Yahoo UK’s ‘The Royal Box:’ “[The Queen] always chooses a brooch with care, that is definitely true.”
As she points out, Her Majesty chose Queen Mary’s True Lover’s Knot brooch (believed to be symbolic for love) for her grandson Prince William and Kate Middleton’s wedding in 2011.
“The brooch that she chose to wear on day one of Donald Trump’s visit last time was vintage floral brooch that had been given to her by Barack Obama.
“Now that is clearly no coincidence, definitely no coincidence. Is it an insult or is it a tribute? You could argue it both ways.
“I mean it’s fair enough to say that we know Trump and Obama absolutely loathe each other, so I think it is fair to say there was a little message there.”
The Queen had an audience with the Archbishop of Canterbury and the Grand Imam of Al-Azhar at Windsor Castle on July 12, 2018 - the day Mr Trump arrived in the UK.
According to From Her Majesty’s Jewel Vault, the 14-karat yellow gold brooch was bought by the Obamas from the vintage selection at the Tiny Jewel Box jewellery store in Washington.
On the day the Queen met Mr Trump and Melania at Windsor Castle, she donned the the Queen Mother's Palm Leaf Brooch.
McAndrew says: “That is the brooch that the Queen Mother wore to the Queen’s father’s funeral and then the Queen inherited it.
“People who were scraping the barrel a little bit for messages said it’s hardly a brooch that has got happy memories, so it’s a brooch she’d wear to something she doesn’t want to go to.
“It is a bit of fun but you can guarantee that Twitter will be alight with people waiting to see what brooch [she wears].”
On the final day of the president’s visit to the UK, the Queen wore the Sapphire Jubilee Snowflake Brooch (a gift from the Governor-General of Canada in 2017) when she met with King Philippe and Queen Mathilde of Belgium at Windsor Castle.
McAndrew says: “Again, you could say that it’s a tribute to North America or you could say it’s because she likes the Canadians and she doesn’t like Trump.”