Metro protectron

Metro Protectrons are Protectrons found in metro stations that will ask for a Metro Ticket from the player when activated. If you do not happen to have a ticket in your inventory, the Protection will attack you. After checking your ticket, the Protectron will remain friendly to you, and will walk around the metro station attacking any enemies such as Raiders, Feral Ghouls, etc. It should also be noted that there are similar Protectrons in Super Duper Mart and in the Old Olney sewers that ask for employee ID. The Old Olney Protectron will not, despite its repeated warnings, attack the player (Not always true for the Xbox). The ID for the Super Duper Mart Protectron is on the Protectron's Terminal, and the ID for the Old Olney is in a Skeleton's hand, near the robot. One of the first protectrons can be found during the quest Following in His Footsteps. He can be found in the entrance of the metro, where it's inside the chamber. There is a Metro Ticket nearby so remember pick it up when it ask you for a Ticket.

If you enter Dupont Circle Station by the Collapsed Car Tunnel, you'll see a de-activated Protectron inside the room you're in and also two Super Mutants in the other room by the metro gate. If you activate the Protectron it will instantly walk to the super mutants and ask them for Metro Tickets. They will begin to mock it, calling it a "stupid robot". Despite this, the Protectron will keep asking for tickets, then one of the Super Mutants will say "Silly robot... Smash it!" and they will start attacking it, and the Protectron will most likely get destroyed.