Definition
When iron or steel is exposed to oxygen and moisture, it forms a reddish-brown coating called rust. Something is 'rusted' when this process has occurred. Think of it like a metal's version of getting a sunburn โ๏ธ. The rust weakens the metal, making it brittle and prone to breaking. Imagine a shiny bike left out in the rain transforming into a crumbly mess. This is why it's important to protect metal from the elements; otherwise, it will become rusted over time.