Why is the statue of liberty made of copper?

Copper is a very durable material when exposed to weather and is soft enough that it can be easily molded to curved shapes such as those in the Statue of Liberty. It is also traditionally used in buildings for complex roofs, so there would have been trades people available trained to use it.
Other metals that can be molded are lead but it does not have the attractive verdigris color, and gold much is more expensive