Can I paint white and dull steel siding?

Yes. You can paint it with Rustoleum paint. Be sure to sand, rinse and let dry before painting. If you don't sand it with metal sandpaper,the paint will peel.

I've never had aluminum siding but I found a good article on how to paint it.

https://www.wikihow.com/Paint-Aluminum-Siding

Hi Marilyn. I'm Cindy. Yes, metal siding can be painted. I recommend taping and covering windows, doors, etc. and use a paint sprayer. It will make this job a lot easier. Be sure to use paint made for this exact purpose. Best of luck to you.

You will definitely need to wash it down. The paint steel siding is coated with "chalks". Meaning that over time the paint "powders" off. Just rub you hand over ti and the you'l get some chalkiness on your hand. Then you need to prime with a good stain blocking primer. Use an exterior paint made for painting metal. Steel siding expands and contracts. You don't want the paint to alligator,crack, or peel.

I'd be very very careful and test a small area where it won't be seeing very well and be aware that may not last on your siding the way it went on other surfaces