Rust-Oleum's website says that their products can be applied to metal surfaces such as gutters, but there's some debate on whether or not it can withstand the test of time. This question is somewhat subjective, as it depends on what you plan to use the paint for. If your purpose is to paint your gutters to match the color of your house, then it will probably do the job just fine. However, this argument is down the drain if you're planning to use the rust-oleum paint to help prevent further rusting or deterioration of the gutters themselves. In this case, the paint would probably last much longer if a different material were used, such as galvanized steel. I've found several forum posts where people have tried this method with varying results, with some stating that rustoleum paint did not last and others claiming that it lasted just fine. I think my recommendation would be to try it out on a small portion of your gutters first, and see how it goes.