That's an excellent and very practical question. As someone who's dealt with more than a few bins over the years, I can tell you that the finish's durability is a make-or-break feature. The good news is that most modern metal outdoor trash cans—especially the better-quality ones—use finishes specifically engineered to hold up remarkably well against everyday scratches from branches, pets, or being dragged across a patio.
The champion here is powder coating. This isn't paint; it's a dry powder electrostatically applied and then baked on. The result is a thick, hard, and uniform layer that's highly resistant to chipping and scratching. It's far tougher than traditional liquid paint. You might see fine, superficial scuffs over time, but these rarely penetrate to the metal underneath, which is what prevents rust.
Another common finish is porcelain enamel. It's incredibly hard and offers fantastic scratch resistance, similar to a cast-iron bathtub. Its main weakness is impact—if you hit it hard enough with a sharp object, it can chip.
For light scratches or scuffs that don't expose the bare metal, a simple cleaning and maybe a touch-up with matching appliance paint (if provided by the manufacturer) will do the trick. The key is maintaining that protective barrier. Avoid using abrasive pads or harsh chemicals when cleaning.
So, to directly answer your question: a high-quality powder-coated or enamel finish on a metal bin holds up against scratches very well. It's designed to take the bumps and scrapes of outdoor life while keeping the bin looking good and, most importantly, rust-free for many seasons. Just choose a reputable brand known for its coating process.