My question is similar to that of Puddin' Man's below. I also have
non-insulated metal garage doors (probably aluminum) with original
factory finish. They're nine years old and have become chalky. We live
in the desert southwest, and the doors get about 6-7 hours of sun
(depending on the season).

We contacted two professional painters. One said we should definitely
use an oil-based (alkyd) paint because it will hold up better with our
heat and sun. The second painter said we should definitely use acrylic
(latex) paint, because oil paint dries rigid and, since the aluminum
doors have a slight "give" to them, the oil paint would end up getting
hairline cracks. He said acylic would be better since it's more
flexible.

Does anybody have experience with oil paint cracking on metal garage
doors? Any other comments?

Thanks... Steve