Players have always used some form of head protection over the years, from full backs to props.
Helmets are usually made from light plastic materials which can take strong tackles, often used by front row forwards to prevent blows to the head and damage to their ears.
The most important thing to remember if you want to wear head protection is to make sure it is comfortable - otherwise it will cause yourself unwanted pain and injury.
If you are a front row forward, make sure the cap will not cause you any problems in the scrum.
If you can, scrum down with a friend when you are trying on different models.