In this Shield 5e spell an invisible barrier of a magical force would be appeared and even protects you. Until your next turn starts and you also have a +5 bonus to AC, which is including against the triggering attack and also you do take none of the damage from the Magic Missile.
Did you check mage hand 5e spell
Attributes Of Shield 5E Spell
|Casting Time||1 reaction, which you take when you are hit by an attack or targeted by the magic missile spell|