Place your metal sheet on a hard raised surface such as a desk or woodworking station.
Use an object to trace a circle onto the aluminum sheet with a thin tipped marker.
Position your body for leverage by pulling part of the aluminum sheet off the desk when you cut. Have one hand on the saw and use the other to hold down the metal. Do not try this unless you have experience with this type of work as it can be very dangerous.
Use the table saw to cut around your outline by applying downward force onto the metal, moving in a forward and backward motion.