Enemies in Horizon Zero Dawn are listed here. The robots that wander the landscape do so under their own ecological machinations, with their reasons not totally clear. They behave in a manner similar to animals in the wild, with herd behaviors present. There is a corruption that is spreading through the machines, marked by a black ooze. When corrupted, a machine behaves unpredictably, and is prone to violence.
Aloy will make use of various Weapons to subdue the machines. Machines can be restrained with a Ropecaster or traps, or brought down by scanning for their elemental and armor weaknesses. See the Combat page for in depth info on how Aloy can approach hunting the robots.