Steel roofing materials for residential applications is very lightweight with the product weighing about 1.5 pounds per square foot when installed. The products are initially produced in giant rolls at the steel mills. They are then coated at the steel plant with a metallic coating (galvanization) to prevent rust. The rolls are then painted at a coil coating plant using high-speed paint lines that bake on the coating. The painted coil is then shipped to a roofing manufacturer where it is formed into long panels by a process called rollforming or they are stamped into individual shingles using large presses. Some of the drawbacks to metal vs shingle is potential damage from hail or other heavy debris as it will likely get dents or bends in it vs shingle, which can also be easily replaced. 

Standing Seam: 

Aluminum is often a recommended roofing material substrate in heavy salt spray environments. This will occur where there is a lot of wave action in salt water near the ocean. In many inland salt water situations steel with metallic coatings performs very well if there is not a lot of wave action — intercoastal area of Florida and the Southeastern U.S. 

Most residential metal roofing has a paint coating applied to the outside of either the aluminum or steel plus metallic coating. One of the big misconceptions is that metal roofs will last longer, and will withstand hurricane winds better than shingle. As a generic rule that somewhat applies, but truthfully if the wind is strong enough (130+) it too will rip off. So they actually are about the same strength because shingle can bend.

V Crimp: