Update (1240ET): 

France's former finance minister, Bruno Le Maire, who was appointed head of the Ministry of the Armed Forces on Sunday, announced his resignation less than 24 hours after taking the job, amid ongoing political turmoil that rattled stocks and bonds in Paris on Monday. 

Bloomberg noted, "President Emmanuel Macron's decision late Sunday to return Le Maire to a ministerial post, in charge of defense, sparked a political backlash, including from within the administration." 

By Monday evening, Le Maire wrote on X that President Macron accepted his resignation and expressed hope that his departure would help efforts to form a new government, reaffirming his ongoing commitment to serving France and the public interest:

My decision to join the government was taken solely out of a sense of duty, in grave geopolitical circumstances, to serve France and the French people.

I note that my decision is provoking incomprehensible, false, and disproportionate reactions in some quarters.

No individual situation must block the proper functioning of the country and our institutions.

Under these conditions, I proposed to the President of the Republic at the end of the morning to withdraw from the government without delay and to transfer my responsibilities as Minister of the Armed Forces to the Prime Minister.

The President of the Republic has accepted my proposal.