That's a common eyesore, but thankfully, it's often a fix you can handle yourself! Rust on a metal trash can is usually surface-level from moisture and debris. Here are a few simple, effective methods using items you probably already have.
For light to moderate rust, white vinegar is a superstar. Soak some paper towels in plain white vinegar and press them onto the rusty areas. Let them sit for an hour or two—the acetic acid works to loosen the rust. Then, scrub with a stiff-bristled brush (an old toothbrush works for small spots) and rinse. For tougher stains, make a paste with baking soda and a little water or vinegar. Apply it, let it sit for an hour, then scrub and rinse thoroughly.
Another great option is lemon juice and salt. Sprinkle coarse salt on the rust, then squeeze fresh lemon juice over it. The combination creates a natural reacting cleaner. Let it sit for a few hours before scrubbing and rinsing.
After cleaning, prevent future rust by drying the can completely. A quick spray with a mild soapy water solution and a rinse every few weeks can also prevent buildup. With a little effort, your bin will look much better!