Accidentally frozen cans, such as those left in a car or basement in sub-zero temperatures, can present health problems. If the cans are merely swollen-and you are sure the swelling was caused by freezing-the cans may still be useable. Let the can thaw in the refrigerator before opening. If the product doesn't look and/or smell normal, throw it out. DO NOT TASTE IT! If the seams have rusted or burst, throw the cans out immediately, wrapping the burst can in plastic and disposing the food where no one, including animals can get it.
(Taken from the USDA Website)