Various different metals and alloys are act as gold substitution to create fake or counterfeit gold bars or gold coins, depending on the reason for, and nature of, the particular fake.
At early times, lead is commonly used to make fake gold coins, we cannot remember when we last saw a lead counterfeit of a gold coin or bar, it is quite an infrequent occurrence. Lead would be too soft, feel wrong, and sound wrong. It would therefore be a very easily detectable fake, and probably not worth the effort of forger setting up any serious volume production.
Platinum has been used to make counterfeit gold coins, before its value rose to exceed that of gold.
The most frequently used for fake gold products is tungsten, most of us may have ever seen tungsten fake products, and it is so realistic. Unlike lead, tungsten is denser than almost all other gold substitution, and almost the same as gold, hence whether something is made of gold is extremely hard to spot.