well, i freeze just about everything (including muffins and other baked goods: breads, cakes, etc).
i usually defrost items in the fridge overnight and then heat up in oven or microwave. but i have put denser items into the oven frozen like breads (bagels & pretzels are the most suited for this method, i find). if your muffins are on the dense side, this could probably work, otherwise i say defrost in fridge overnight.
either way, yes! you can freeze muffins lol