Speaking of mayoral elections, France has jumped straight to pre-election maneuvering long in advance of the actual vote (unlike the European election, but that's a much more popular and important election). All of the mayors face polls on the same day, which the Germans find odd apparently.
Macron's party is obviously courting a number of mayors (mostly from the right wing Les Républicains who are in disarray after their European flop). Already 70 LR mayors signed an op-ed to say they were open to it. It's not just on their right, they're also probably throw their support to Lyon's mayor G.Collomb who is a former Socialist but he had already changed allegiance back before Macron's election, he was his first Minister of Interior. There's no confusion which side LREM has more affinities with.
As someone noted it's a bit of an implicit admission that LREM can't just suddenly grow grassroots by itself. As you may remember, the French National Assembly saw almost unprecedented level of personnel replacement and political débutants getting their first mandate but it hasn't really rejuvenated politics in France, the system already is biased to the President and Macron leant really hard on keeping as vertical as ever. LREM targets 10k local officials (from their current 2k) after the election.
Far right Rassemblement National is expected to consolidate his holdings and gain more cities (in a strategy called "radiation" by the party or "flooding" by others). I mentioned this before but the RN only has a dozen mayors or so (counting Béziers where the mayor Robert Ménard -yes, the co-founder of Reporters Without Borders- is non affiliated officially but has the backing of RN on the council) out of 36000 in France when the current agonizing Communist Party still has 750 or so. It never made inroads locally, almost never managed to win two mandates back to back in the half of dozen cities it had in the past. But it looks like the containment will break down alongside the decaying of the two former major parties.
A number of LR mayors, especially in the south-east, will probably go on the road of allying to RN to achieve majorities.
The Green party is still high off its results in the Euro election and has annoyed a lot of people by openly declaring they intend to win more cities by themselves and that basically being suppletives for the Socialist doesn't interest them as much. I mean it's not wholly unjustified but it's a bit of a crapshoot that the Euro election results will map to local elections.
Speaking of Socialist, the polls from Paris, that they are holding since 2001, are souring a bit as it seems the incumbent -Anne Hidalgo- could lose to any LREM candidate. It's vitally important for the PS they keep Paris (and not just for the optics of losing the most important city in the country) so they'll probably throw everything they could to the Greens to keep that alliance going.