There are 13 companions available to the player in Fallout 4. All of them except for Dogmeat will react to the player's decisions with either approval or disapproval. Reaching maximum affinity with them unlocks a special perk that will boost the player's performance. Additionally, companions can be romanced if the play so chooses after reaching maximum affinity; this allows the player to access the Lover's Embrace, which increases experience gained for a short time after sleeping in a bed near their lover.
Companions who have hands come with a ranged weapon that has unlimited ammunition. This weapon does not show up in their inventory. However, the player may equip them with any other weapon, but that other weapon will require ammunition. If they run out of ammo, they will switch back to their unlimited ammo weapon.