without damaging metal, how to attach metal house numbers to metal sheathing
Automotive trim tape.

For example, 3M 38583 (I'm not in any way associated with 3M, but I did just buy a roll of the stuff for the automotive purpose it's intended for.)

Weatherproof, lasts a long time, and if you need to remove them you saw them off with a section of fishing line and then rub the remaining adhesive off (they even make a special tool for THAT job for the automotive application, but I haven't bought one as I doubt the scale of my job calls for it.)