Way of cold iron

Monks of the way of cold iron are smiths and warriors

Level 3: Bonus proficiencies

at 3rd level you gain proficiency with medium armor heavy armor and smiths tools

Level 6: Master of iron

You can command metal to do simple things like move out of a space to create a hole our dissolve 

Level 11: Iron shield

You use your reaction to create a iron shield that halves a melee or ranged weapon attacks damage

Level 17: One with iron

you have such control over metal that you can command it this manifests in 2 distinct ways { 1. iron cage you command the metal to form in to a cage around 1 creature of your choice the cage is around for 1hour } { 2. metallic shields you use your reaction to conjure 2 shields that effectively cast mage armour } you can use these a number of times equal to your proficiency bonus a minimum of 1once

Level 3: Iron control

your control over metal is strong you gain a special ability iron meld you can meld through metal as if it were water