An exceptionally hard piece of food, a bone or even a piece of silverware gone awry in the drain will cause the disposal to rattle loudly. Turn off the power to the disposal and check for a blockage by carefully inserting a pair of metal pliers or tongs into the disposal opening.
Over time, screws that secure the disposal to the underside of the sink may come loose. Check the connections and tighten them with a screwdriver.
The garbage disposal may rattle from a broken blade or broken motor component inside the unit. In such a case, the disposal must be removed from the sink and taken out for repair or replacement.