Steel roofing is by far one of the most long-lasting and durable roof systems available. When the details are thoughtfully tackled a steel roof will perform well for many decades.
Some steel roofs have extra large obstructions, such as double skylights or triple-flue chimneys, which can impede the flow of water. In some cases, water could pond or freeze up behind these obstructions, causing a leak.
A simple solution: build a saddle.
A saddle is a feature constructed behind a large obstruction on a roof in order to divert water properly. Because it is built on a slight angle, the roof flashing very effectively sheds water. A saddle is primarily for function but can act as a subtle aesthetic compliment as well.
Pictured below: saddle installed above double skylight on a steel roof.