Roof painting-How do I paint a metal roof properly??

You probably did the barn when it was above 80° . The paint dried so fast that it didn't have time to adhere to the metal. Or you didn't clean and rinse it well enough. I used Rust-Oleum paint after cleaning the roof well and it has lasted 10yrs so far.

Hello Theresa! Here is information on the process to successfully paint that metal roof:

http://homeguides.sfgate.com/paint-galvanized-metal-roof-sherwinwilliams-97939.html

Also you need 2-3 thin coats . Allow time to dry to touch.

Go to a hardware store or Homedepot or Lowe's, check in the paint department. I think you need some sealer after you paint, so the elements don't destroy your paint job. Good Luck!

You can use an airless spray painter https://www.youtube.com/watch?v=g8gdDqvbDWo