Rub a steel brush over and around the hole to remove any loose rusty gutter pieces. Paint the area with a rust-inhibiting paint that matches the color of your gutter. Wait three to four hours for the paint to fully dry.
Apply a 1/8-inch thick layer of rubber gutter cement over the hole. If the hole is less than 1 inch in diameter, this is all that is needed. If the hole is larger, it will need additional coverage.
Cut a piece of heavy aluminum foil, plastic or sheet metal so that it fits the area being patched. Put on a pair of work gloves and press the aluminum foil into the rubber gutter cement. Smooth it out to remove air bubbles and wrinkles.