Monks of the way of the Steel body have steeled their minds as to make their thoughts impenetrable, and over months of training they have learned to transfer their Stell like mental state to encompass their entire body to make themselves impenetrable.

Steel Body

When you gain this skill at level 3 you have the ability to change the top layer of your skin into solid steel using 3 ki points. With this you gain a +3 bonus to your ac. You also deal extra bludgeoning damage equal to half your monk level rounded down. you also take an extra d10 damage against lightning damage. This stays active (until it either runs out or you end it using your bonus action) for up to an hour equal to your wisdom modifier (minimum 1). You also lose your unarmored movement and half swim speed. You also have disadvantage on stealth roles

Lightweight material/ Protective surface

• At level 6 you regain your unarmored movement skill and swim speed
• You no longer have disadvantage on stealth roles

Protective surface

• At level 6 you gain resistance to bludgeoning piercing and slashing damage made by non-magical Weapons

Carbon alloy

• At lv.11 you gain the ability to have an even tougher hide. When you activate your steel body ability you can spend up to 5 extra ki points to become tougher to hit. For every 1 ki pint you spend you get a +1 to your AC
• You also gain resistance to fire damage

Steel defender

• At lv. 17 you gain the ability to protect an ally within 5 feet of you by using (2 ki points and your reaction) to impose disadvantage on an attack against them by forming a small steel shield in front of them. You also gain the ability to share your current armour buff with an ally by using 

(4 ki points)