Metal shingles are very durable and are perfect for hard climates. They are also great because they do not need any hard maintenance. They just need an yearly checkup and maybe a few repairs because of the thermal movement.
Remove all the debris from the roof. Branches, leaves and dust will gather on your roof and can damage it. Do this more often if you have trees around your house. Also the sticky substance from the trees can warp the shingles. Use a power washer and some cleaning products to keep your roof clean.
Rust is the biggest enemy of metal shingles. You should remove it immediately as you spot it because it can extend to the entire roof and can damage its structure and also covering. Use a wire brush or a light sander to remove it. Apply rust resistant paint or primer on the affected areas.
When new, shingles are coated with a protective paint to extend their durability. But in time, this coating will get weared and the shingles will remain unprotected. It’s important that once in a few years you apply a new layer of coating. To further protect the shingles.