Monks who take this path are rare due to the strain needed to put into their legs.  These monks have managed to harness their Ki into harness a steel-like material around their legs, giving them immense powers as they continue to train with it.  Most monks who take this path trade speed for stronger strike.  Even the weaker iron leg monks are said to be able to cut big trees in half with a single kick of their legs.

Iron Body Arts

Starting when you choose this tradition at 3rd level, you've learned to harness your ki into your legs forming a coat similar to steel.  As a bonus action on your turn, you can you can expend 1 ki point to activate your iron legs to gain one of the following benefits.  This bonus lasts for 5 minutes.

• You gain a +1 to AC
• Your unarmed strikes deal force damage
• Once per turn you can add your wisdom modifier to the damage of an unarmed strike

Shatter Step

when you hit a creature with an unarmed strike, you can use your bonus action to activate Shatter Step:

• You immediately move up to 10 ft away without provoking opportunity attacks.

• At the end of this movement, you deliver a concussive step. Each creature within 5 ft of your new position must succeed on a CON saving throw (DC = your Ki save DC) or take 1 of your martial arts die of thunder damage and have its speed reduced by 10 ft until the start of your next turn.

• A creature that succeeds takes no damage.

You can use this feature a number of times equal to your proficiency bonus and you regain all uses when you finish a long rest.
You can also spend 1 Ki point to use it again after expending all uses.

Iron Strikes

Your iron legs allow you to deal extra damage when you move faster.  Whenever you use flurry of blows and hit someone with an unarmed strike, those attacks deal extra damage equal to 1 of your martial arts die.  You can also choose to expend 1 Ki point to either push them 5 ft or force them to make a strength saving throw or be knocked prone.

Heavy Blow

Beginning at 6th level on your turn, when you attack, you can forgo one attack so your next unarmed strike that hits deals extra damage to 2 of your martial arts die. ( this feature works with flurry of blows ) When you hit someone with this feature, they need to make a STR saving throw or be knocked prone.  As well, you can expend up to 3 Ki points to get additional effects with this attack.

1. You deal extra damage equal to the amount of Ki points you expended of your martial arts die.( this means if you expend 2 Ki points but put one of them into this effect, you deal 1 of your martial arts die in additional damage )
2. You push the enemy 10 ft away per Ki point expended for this effect.
3. You make an attack roll against an amount of creatures within 5 ft of you ( other than the one you attacked ) equal to the amount of Ki points expended for this effect. (similar to feature 1 )

Iron Resillience

At 11th level you have learned to expand your iron legs all over your body.  As a bonus action on your turn, you can spend 3 Ki points and for the next minute, you gain the following effects.

• You gain resistance to slashing, piercing, and bludgeoning from nonmagical attacks or you gain a resistance to thunder and force damage
• You cannot be forcibly moved ( you’re still affected by gravity.
• you have advantage on saving throws to avoid being knocked prone
• You gain temporary hit points equal to your monk level + your wisdom modifier.  When you lose these temporary hit points, everyone within 5 ft of you makes a STR saving throw or take 1d10 force damage on a failed save, half as much on a success.

Iron Tempest

At 17th level, you've honed your iron legs enough to create your own tempest by slamming them into the ground.  As an action,  you create a tempest around you and everyone in 20 ft of you makes a CON saving throw.  On a failed save they take 8d10 force damage, 8d10 thunder damage, and they are knocked prone.  On a success they take half as much damage and aren't knocked prone. You can use this once per long rest.