Rust is a reddish-brown substance that forms on iron or steel. It appears as a rough coating on the surface of metal. Rust is commonly seen on objects like tools, fences, and outdoor structures. It changes the appearance of the material.

Rust is found in many places around the world, especially in outdoor environments where metal is exposed. It affects iron-based materials over time. Rust is part of how some metals change when left in certain conditions.