In hockey, a cage is constructed of a metal or mesh lattice attached to the front of the helmet, designed to prevent injury to the face or head.
Cages are used primarily in amateur and college ice hockey and
do not see use in the NHL, although many goalie helmets have a
similar cage-like structure for protection.
Instead of cages, the NHL typically uses visors or shields that cover the upper portion of the face (mostly in order to protect the eyes). While they are not required, shields are "strongly recommended" by the NHL and most players do wear some form of shield or visor.