Helmets used for different purposes have different designs. For example, a bicycle helmet must protect against blunt impact forces from the wearer's head striking the road. A helmet designed for rock climbing must protect against heavy impact, and against objects such as small rocks and climbing equipment falling from above. Practical concerns also dictate helmet design: a bicycling helmet should be aerodynamic in shape and well ventilated, while a rock climbing helmet must be lightweight and small so that it does not interfere with climbing.
Historically, helmets have been made from a wide range of materials, including various metals, plastics, leather, and even some fibrous materials such as Kevlar. Ancient and medieval helmets were usually made of metals, often bronze, iron or steel
Helmets of many different types have developed over the course of human history. Most early helmets had military uses, though some may have had more ceremonial than combat-related purposes.
Helmets of