We have seen in the TV series Rome and several movies the centurion helmets.  
 
This is the miniature replica of the Galea centurion helmet, typically made from a combination of materials to ensure both durability and protection:
Bronze or Iron: The primary material for the helmet’s structure, providing strength and protection against weapons.
Leather: Often used for the inner lining to provide comfort and a better fit for the wearer.
Horsehair or Feathers: Used for the crest, which was both decorative and functional, helping to protect the head and the neck, and also to identify the rank of the centurion on the battlefield.
These materials combined to create a helmet that was both practical for combat and symbolic of the centurion’s status and authority within the Roman army.
 
Centurions were responsible for leading centuries, which were units of about 80 soldiers.
Centurions played crucial roles in many significant battles and campaigns throughout the Roman Empire, including:
The Punic Wars against Carthage
The Gallic Wars led by Julius Caesar
Various civil wars and conflicts within the empire.
 
In terms of authority and position within the legion:
Centurions were crucial to the structure and effectiveness of the Roman military. They were the backbone of the army, ensuring that orders from higher command were executed efficiently.
Each legion was divided into 10 cohorts, and each cohort contained 6 centuries. This means a legion had around 60 centurions.
The most senior centurion of a legion was the Primus Pilus, who commanded the first cohort and had significant influence and authority.
Centurions were respected for their experience and leadership skills, often rising through the ranks due to their bravery and tactical acumen.