He did use a lot of other metals to begin with but found that while using gold, the beam of particles was scattered less by gold because it can be made into a very thin sheet(gold is the most malleable metal).
Due to the high malleability of gold, sir rutherford used it.
Gold Foil can be made very thin, a few atoms wide. Thus it is easier for the beam of alpha particles to pass through the foil, rarely deflected by the central nucleus. The deflections were measured by a circular sheet of zinc sulfide (ZnS).
Hope it will help. :-)