internaughtfull wrote:
I have a metal roof on an outside porch attachment [no ac, no heat]
and the roof gets a lot of condensation on the underside in the
morning, and sometimes drips and gets things wet.

The water in the room air is condensing on inside of the cold roof.
Surface treatments to the roof will not fix this. Either lower the
temperature of the inside to match the outside, or dehumidify the
room air to an extreme point, or insulate the underside of the roof.

Una