Your best bet is to thoroughly clean the rusted area and then apply a rust-inhibiting primer. Once the primer is dry, you can then paint the fence with a rust-resistant paint.

There are a few ways to fix a rusted metal fence: -Remove the rust with a wire brush or sandpaper until the metal is smooth. Then, coat the metal with a rust-inhibiting primer and paint. -If the rust is too extensive, you may have to replace sections of the fence. -You can also try using a rust converter to stop the oxidation process and then coat it with primer and paint.