I know the nazis occupied the country and I assume they had soldiers under control and without weapons, but couldn't the Allies have freed / armed them? Whenever I read (not that much tbh) about the British and Americans fighting in France I don't see many mentions of the French, except for some support provided by the resistance.
I know your question is about metropolitan France, but I can speak to Vichy Syria: The embarrassing aspect of this and why it's probably not very much discussed is that not only were French Vichy troops still armed, not only did they not immediately defect when the British and Free French arrived, but they actually fought quite intensely against the British and Free French Forces in a campaign that produced thousands of casualties over the course of June and July 1941. The British, eager to secure an immediate armistice with the Vichy forces in Syria (who refused to recognize the Free French at all), signed an armistice that excluded the Free French and prevented them from fraternizing with captured Vichy troops. De Gaulle, probably out of deep political embarrassment, skipped town to Brazzaville until after the deal was signed, effectively so that he could deny any responsibility for it.
After the liberation of France, the leader of the Vichy forces in Syria, Henri Dentz, was sentenced to death, but DeGaulle commuted his sentence to life imprisonment.
You can read about this, for example, in De Gaulle by Julian Jackson (which might well also answer your question about Metropolitan France, but I have to confess I've only skimmed the parts of the book relevant to my areas of interest :)
edit: minor clarification