What kinds of materials are used for ballistic helmets?

Here are some of the main materials for helmets to date:

Kevlar

The most prominent material for bulletproof products, Kevlar is made of super durable plastic that can withstand ballistic penetration even better than steel and other materials. In fact, it's 5 times stronger than steel on an equal-weight basis. Kevlar resists heat, has great tensile strength, and is lightweight.

UHMWPE

Ultra-high molecular weight polyethylene (UHMWPE), also called Dyneema, provides a great bulletproof ability when combined with other materials.

While it might not be as good as Kevlar when it comes to creep resistance, it has its own advantages such as its much lighter weight and incredible strength- 15 times stronger than steel!

Steel

US Army infantryman wearing a Brodie Helmet

Steel, as well as other materials, was mainly used in earlier helmets before previous decades’ scientifically formulated materials appeared.

Ballistic helmets may also be made from other materials including

fiberglass - can be mixed in the helmet’s shell
Twaron - in the same materials family as Kevlar
carbon fiber - strengthens some helmets by combining with other materials like Kevlar
WHAT KIND OF ACCESSORIES CAN YOU USE ON HELMETS?  
Most ballistic helmets allow the flexibility to secure accessories such as:

Side Rails

You’ll need side rails if you want to mount something alongside your PASGT helmet. Side rails, with their holes and fastening systems, can interlock devices for different purposes, such as communication gadgets and oxygen masks.

NVG Shroud

US Navy aviator using helmet-mounted night vision goggles

If you need to mount night vision goggles to your helmet, you'll need an NVG (night vision goggles) shroud. This gear allows you to attach the goggles to your forehead and flip them toward your eyes when needed.

Fitting Mechanisms

Different accessories can be incorporated into a helmet to cater to the fit of its wearer. For example:

Chin straps and retention systems adjust to the circumference of your head to keep the helmet in place.
Comfort pads serve as cushions and keep the grip of the helmet.
There are also entire helmet liner systems with features such as sweatbands to absorb sweat.