A shield is an item used mainly for defense, while a sword is used for offense. As always preferred, shields are used to block certain deadly attacks from opponents like arrow hits or sword slashes and stabs. They are sometimes carried by gods and demigods. When holding a shield and wearing armor, it has been described by Percy as being "dressed for defense" making playing offense tiring. Shields are sometimes used to form a Phalanx (Greek) or Testudo (Roman). Though the uses were very different between the two, Greek shields called "hoplons," they would have the right side of the neighboring shield to overlap the left side and held by an argyle grip (a handle on the far side with a leather belt at the center holding the forearm). Roman shields called "scutum" were placed one next to the other and held by one hand at the center.
- Roman shields when in the testudo formation require the second and forth rows to carry their shields over the soldiers heads. This protects the unit from missiles such as javelins, arrows, and such.