Yup, just make sure the dimmer is rated above 500w. Typical household dimmers are rated at 500w to 600w, which should work but might burn out in a short time. I would suggest spending a couple bucks more and getting a better dimmer that can handle 700w to 1000w You should be able to get them at Home Depot or some similar store.

Is your light on an existing switch or how do you control it? If it's not in a "dry" area you will have to go with an exterior dimmer costing even more money.