How many cans would I need to paint an outdoor metal bench?

Thank you for reaching out! Our Rust-Oleum Stop Rust Protective Enamel Sprays cover approximately 10 ft² per can, so the best way to estimate the number of cans needed is to measure the bench and get the rough square footage. If the metal bench has slats and other narrow surfaces, you can expect to have some paint loss when applying, so be sure to get a bit more than you anticipate needing. - Rust-Oleum Product Support 2