Mr Macron, a former banker, is seen as a political outsider, having never run an election campaign before.
After topping Sunday's vote, he is now favourite to win the run-off on 7 May.
It is the first time in six decades that neither of France's main left-wing or right-wing parties has a candidate in the second round.
With 97% of votes counted, Mr Macron stands at 23.9% with Ms Le Pen on 21.4%.
Their nearest challengers, centre-right François Fillon and hard-left Jean-Luc Mélenchon, fell behind, with just over 19% each.
