May, acting as host of the ceremony, received Macron on the Normandy memorial site at about 8.30 a.m., reports Efe news.
In his speech, Macron highlighted the sacrifice British soldiers made in their efforts to free France of Germany's occupation.
"The force of our friendship will outlast current events," the French President said, adding that both nations should be proud of the results that had been achieved.
The event was taking place at the British Normandy memorial which is built on a hill in Ver-sur-Mer, which overlooks the beach British troops landed on on June 6, 1944.
A memorial monument that pays homage to the thousands of soldiers that took part in the largest seaborne invasion in history will also be inaugurated.
This monument will be a powerful symbol that will unite our nations, Macron said.
May thanked Macron for his efforts in making the memorial monument possible, adding that it was important for the veterans who were part of "a very special generation".
"It is incredibly moving to be here today, looking out across beaches where one of the greatest battles for freedom this world has ever known took place - and it is truly humbling to do so with the men who were there that day," said the outgoing UK leader.
May also highlighted the bravery that was displayed by soldiers on the day, saying that nobody could have been sure whether events would have unfolded as they eventually did.
"As the sun rose that morning, not one of the troops on the landing craft approaching these shores, not one of the pilots in the skies above, not one of the sailors at sea - knew whether they would still be alive when it set once again."
The main event will take place at the Normandy American Cemetery and Memorial with US President Donald Trump in attendance.
( With inputs from IANS )