From this article you will gather some input on standing seam metal roof hail damage.
The roof integrity is a constant concern for all the property owners and there is a popular myth that standing seam metal roof can be easily deteriorated by hail. To allay the fears Roof Experts state: metal roof will withstand hail. But if the house is located in an area where this nature phenomenon is very frequent, then strong hail might make dents on the aluminum or copper roof, as they are soft metals, easily prone to physical impact. Steel standing seam on the contrary will better withstand such weather.
What size should hailstones be in order to damage the pitched roof? It depends on many parameters. First of all, it makes sense to define what is considered damage to the roof. If the roof integrity is not disrupted and there is no reason to think that its service life has decreased, then such damage is not functional. It is especially true if the hail is 1 cm size, has oval shape and no pointed edges.