Sorry, I’ve never been to Montpellier but I believe it’s on the Riviera, although not the most fashionable part. I would think you’d want to at least check out the beach, probably some great people watching. As I said, I don’t know the town, but if it’s your first stop in France, get a baguette and some cheese, sit in a cafe, have a strawberry tart, see if there’s any local museum and do check out the beach. I was just in Nice (as well as Paris) and shocked to discover that the beach there is all little stones! Keep your eyes open and you’ll be sure to see interesting things.