Rusting mainly occurs when a metal is exposed to air and moisture.

The given statement is True.

Rusting of iron refers to the formation of rust, a mixture of iron oxides, on the surface of iron objects or structures. This rust is formed from a redox reaction between oxygen and iron in an environment containing water (such as air containing high moisture levels).

So, it can be said that rusting mainly occurs when a metal is exposed to air and moisture.