Macron’s one-year-old centrist party La République En Marche (Republic on the Move) and its MoDem ally are set to win up to 445 seats in the 577-seat National Assembly.
The result would give Macron one of the largest parliamentary majorities since the end of the Second World War.
Meanwhile, the British Prime Minister suffered a humiliating defeat in the General Election last week, losing 13 seats and failing to reach the 326 majority threshold by eight seats.
The former ruling party in France, the Socialists, which was led by Macron’s predecessor Francois Hollande, took just 9.5% of the vote with allies and are expected to lose 200 seats.
The centre-right Republicans secured 21.5% of the vote, coming in second, and the far-right National Front got 13.2%.
The final result will be declared in the second round of voting next Sunday.
German Chancellor Angela Merkel congratulated the French President on Monday.
“My heartfelt congratulations to Emmanuel Macron on the great success of his party in the first ballot,” Merkel was quoted as saying by government spokesman Steffen Seibert on Twitter.
Following May’s election defeat on Friday, the German government refused to comment “out of politeness”.
Despite Macron’s success, turnout was very low for this round of French elections, with 48.7% casting their ballots compared to 57.2% in the first round in 2012.
It is not the first time Macron has showed up May.
Earlier this month, the French President was widely praised for speaking out against Donald Trump’s withdrawal from the Paris Agreement on climate change while May was condemned for expressing her “disappointment” only.
May’s name was noticeably absent from a joint statement signed by the leaders of France, Germany and Italy.
Things might get even more embarrassing for the British Prime Minister, who is due to meet Macron in France on Tuesday