Rust is a form of corrosion. It occurs on numerous kinds of metals, iron being one of them. Rust forms when iron oxidizes and absorbs water. Rust is brittle in nature.
Iron on the other hand is a malleable and ductile metal. It rusts because it combines with oxygen present in the air along with moisture.
Properties of oxygen are -it is tasteless, odorless and colorless diatomic gas. It combines with iron in the presence of moisture to form iron oxide or rust.