When it comes to the roof, grounding is done with the help of a lightning rod, which is an installation designed to capture the current emitted by lightning and to conduct it safely in the ground. Installing a lightning rod is necessary regardless the type of the roof, because it protects the house from catching fire, and the electric system and electronic appliances from short circuits that could damage them for good.
Devastating effects of lightning on a house may include:

• deterioration of the roof and the building
• damage to electrical and electronic installations
• injury to family members, including pets

In the case of a roof made of metallic materials (metal shingles, corrugated metal, standing seam etc.), many people believe that it does not need grounding, because a metal roof represents itself a network of conductors. It is true that when lightning strikes a metal roof, the current of up to 200kA flows into the roof through a single point. The very high current density will melt the metal in that point, and the homeowner may end up only with a hole in their roof, which can be patched.

Unfortunately, this is not always the case, as molten metal can also fall on flammable materials, such as the wood in the resistance structure of the roof, causing a fire.

Therefore, grounding means better protection, even in the case of a metal roof.  Be sure to have those who work in roofing and have experience with metal roofing like https://ccr-roofing.com/ to install your new roof.