The most malleable metal that exists in its pure state is gold. Gold, also the most ductile metal, is capable of being flattened so that it can measure only 0.000127 millimeters in thickness.
A single ounce of gold can be rolled and beaten thinly enough that it could cover a sheet that measures about 5 meters on a side. Since gold is the most malleable and ductile metal in existence, it has to be alloyed with other metals to be used in jewelry and coins, which require gold to be plated onto them rather than comprising the entire item. Pure gold jewelry and coins would be easily deformed by pressure.