After the ceremony, Merkel and UN Secretary-General Guterres gave the opening speeches at a new peace forum in Paris set up by Macron - with both warning that rising nationalism threatens the rules-based global order.
He urged the leaders present to promise their peoples that the resurgent "old demons" would not be able to return, sowing "chaos and death".
French officials, however, say - without elaborating - there was a misunderstanding by Trump about Macron's comments, noting the USA president told his French counterpart in their Saturday meeting: "I think we are much closer than it seems". The move drew swift condemnation at home, as Republicans and Democrats alike cautioned Trump over the connotations of openly "nationalist" rhetoric. German Chancellor Angela Merkel was positioned in pride of place between Trump and Macron, an eloquent symbol of victors and vanquished now standing together, shoulder to shoulder.
The message was both a call to learn the lessons of 1918, when an armistice was signed that led to another world war with two decades, and a rebuke to present-day leaders who shun the global order in favour of protectionist, nativist policies.More news: Amazon agrees to list iPhone, iPads, other Apple products
During a speech in front of the Tomb of the Unknown Soldier at the base of the Arc de Triomphe, Macron delivered a direct rebuke of nationalism, warning the leaders gathered that a "fascination for withdrawal, isolationism" contributed to the events that caused the Great War.
There was no immediate response from either the White House or the Kremlin to Macron's comments.
The French president also called on his fellow leaders to not forget the lessons of the past. I'm a nationalist, okay?
On Saturday, the White House scrapped the president's visit to a ceremony for fallen American soldiers at the Aisne-Marne American Cemetery and Memorial in Belleau, about 50 miles (80km) from Paris, saying rainy conditions made it unsafe to fly there via helicopter as planned.
Around 70 leaders including US President Trump and his Russian counterpart Vladimir Putin marked the centenary of the 1918 Armistice in the French capital at 11am local time (1000 GMT).
Mr. Trump has repeatedly branded himself a "nationalist", despite criticism from some that the term has negative connotations.
Since then, the US has sent National Security Adviser John Bolton for two rounds of talks with Russian officials, but the only deal announced publicly was a vague agreement for the two leaders to meet again next year, possibly in Washington.
Whether the US and Russian presidents would meet on the sidelines of the ceremonies commemorating the end of World War I had been a subject of speculation in the lead-up to Sunday's events.