Iron sights are a feature in all Medal of Honor series games post-Pacific Assault. It allows for much greater accuracy at range, as a player can easily pinpoint an enemy. Most iron sights have greater zoom when compared to hipfiring. Prior to Medal of Honor (2010), the player is only able to use the Leaning feature while aiming down the sights.
As with real life, sights that use posts and notches should have the target resting on top of them, not in front of them.
Pre-Pacific Assault, iron sights were unusable, although most weapons sights were visible. Instead, a slight zoom increase was provided when the 'aim' button was pressed, in addition to enabling leaning. Scopes were, however, usable.
Medal of Honor (2010) and Medal of Honor: Warfighter allow the player to attach various optics to their weapons, allowing for increased zoom and accuracy when aiming. In Medal of Honor, leaning and aiming are independant of each other by default. The opposite is true in Warfighter.