The mont in the morning or at night or anytime is a marvel.
Mont Saint-Michel is a town with an abbey and church at the top of a steeply inclined walk. It requires walking – and up a steep incline. If you cannot walk for a good distance, you will not make it to see the abbey look at in a picture book and just take my word for it that it is a wonder at the top of that rock.
Normandy is a wonderful part of the world that is worth exploring even more – see Rouen-Caen-D-Day Beaches-Mont Saint-Michel overnight trip.
Take a look at these great tips from the Normandy tourism site.