Roman Helmets - A galea was a Roman soldier's helmet. Some gladiators, myrmillos, also wore a bronze galea with a face mask and a decoration, often a fish on its crest. The exact form or design of the helmet varied significantly over time, between differing unit types, and also between individual examples .
Originally, roman helmets were influenced by the neighboring Etruscans, people who utilised the "Nasua" type helmets. The Greeks in the south also influenced Roman design in the early history of Rome. For instance, the ancestor of the Chalcidic helmet, the Attic helmet was widely used by officers until the end of the empire. Lastly, the Gauls were the peoples who most impacted the design of the Roman helmet hence th popular "Imperial Gallic" type helmets. In addition to this, it is commonly thought that the Gauls also introduced chainmail to the Romans. - Reference: Wikipedia