Way of the Shield allows you to be proficient with shields, with bonuses like unarmored defense/movement and martial arts making an exception for shields.

Shield Technique

Weaponized Defenses

By 6th level, you learned to extend your ki into your shield, granting you the following benefits.   

Magic Shield.

Your attacks with your shield count as magical for the purpose of overcoming resistance and immunity to non-magical attacks and damage.  

Shield Bash.

When a creature misses you with a melee attack, you can expend 1 ki point to make a melee attack with your shield against the attacker as a reaction.

Annoying Percussion

At 17th level, you gain the ability to augment your shield further with your ki and shield yourself and your allies from anything.  

As a bonus action, you can expend up to 3 ki points to grant one shield you touch a bonus to the AC of its wielder. The bonus equals the number of ki points you spent. This bonus lasts for 1 minute or until you use this feature again. While you are affected by this bonus, using Shield Ally will also buff the creature's AC by Mastered Defenses' bonus.

Mastered Defenses

At 17th level, you gain the ability to augment your shield further with your ki and shield yourself and your allies from anything.  

As a bonus action, you can expend up to 3 ki points to grant one shield you touch a bonus to the AC of its wielder. The bonus equals the number of ki points you spent. This bonus lasts for 1 minute or until you use this feature again. While you are affected by this bonus, using Shield Ally will also buff the creature's AC by Mastered Defenses' bonus.