Rust forms when iron or its alloys, like steel, react with oxygen and moisture in the environment. This chemical reaction, known as oxidation, leads to the creation of iron oxide, which appears as a reddish-brown coating on the metal surface. The presence of water, especially when combined with salt or acids, accelerates the rusting process. Over time, rust can weaken the structural integrity of metal objects, making them more susceptible to damage and decay. Preventive measures, such as painting or galvanizing, can help protect against rust formation.