Metal roofs are manufactured and installed in a way that will provide you with many years of trouble-free service as long as some simple things are done when needed. Far to often I see roofs that have leaves piles on them or are just plain dirty. A clean roof is a trouble-free roof. The main purpose of your roof is to shed water off of it during rainy weather. With leaves piled up in the valleys and in other areas, water ends of pooling up and moisture becomes entrapped under the leaf pile. That moisture over time can cause damage to the metal roof. I would recommend blowing off your roof whenever necessary and at least once per year washing it with a mixture of simple green and water.
Other things you will want to check for while on the roof is to check the flashing to make sure it is still watertight and to make sure if you used caulking, that it isn't cracking or pulling away from the wall. Make sure to check the screws to ensure they are still holding. If you follow these simple steps, your metal roof will be trouble-free.