Depending on the amount of rust, use a wire brush and/or steel wool to remove as much of it as you can. Then I would use a Rustoleum spray paint on it.
Prime and spray paint it.
Here are some ideas
You'll want to remove the rust first
You could try spray paint
Try some of the new textured paints. Add a design or stencil or house number on one side.
Check that pin https://www.pinterest.com/pin/458452437066389671/