>Any metal we find after 2000 years is a miracle.

That's not really true. There's regular finds of hoards of thousands of ancient coins that are in excellent condition, esp. Roman coins. You'll find there's an actually quite a large number of ancient metal artifacts archaeologists have discovered if you look into it. Certainly the preservation rate is very low since people tend to guard metal objects and recycle them, but things happen, today archaeologists estimate there's something in the order of 10-30 millions of Roman coins that have been recovered in museum collections and held by private owners.

This depends on the metal, of course, iron preserves poorly as does bronze, so those are rare, but gold preserves extremely well, and silver better than bronze, esp. in drier conditions.