Metal roofs become slippery in dirt or rainy climate. It is even more dangerous than other types of roofing material, such as asphalt tiles. It’s already proven that metal roofs are more slippery than any other roofing. So, you must wear the correct footwear to safely walk on it.  They are so slippery that snow “avalanching” off the roof is a definite hazard in areas that experience heavy snowfalls in winter.  Walking on a metallic roof is way far riskier than walking on any other surface without the proper equipment. It can even cost you your life.