Full Metal Jacket starts out with iconic Robert Lee Ermey playing Gunnery Sergeant Hartman full on humiliating new recruits as they stand resolute. If you know Ermey as an actor you probably know him by this movie alone. He plays a devil of a drill sergeant who is responsible with the task of getting the new recruits ready for the Vietnam War. The main protagonist is "Joker" played by Mathew Modine who is shown throughout the film as an unwilling recruit who goes through camp and war will an almost unrealistic look at things. He sees the most drastic of things throughout camp and the war and without telling more he takes what happens to heart. It borders on extreme exaggeration but maybe that's what Stanley Kubrick was going for. I for one have no account of the Vietnam War or any kind of boot camp so maybe, just maybe he is portraying "real life".
By trying to portray historically accurate events Kubrick relies much on historical and natural Mise en Scene. Every costume and set throughout the film seems to be right on in terms of being true to the time period. Even in the worn torn pacific he manages to make the set third world enough to really portray some sense of utter devastation brought on by war.
The main prop that signifies this entire movie is the helmets of the soldiers. Each helmet has some kind of saying either related to death or war. It signifies how much each soldier has actually been turned into a "killer". Joker's in particular says "Born to Kill" which is what he was trained to believe from when he first stepped into boot camp. What is ironic is that he has a peace sign pin on his uniform. So while he has been "born to kill" he still somewhat believes that there is some kind of peace to be made either with the war or the fact that he has to come to peace with himself. He simply states that it portrays "The Duality of Man" which has a more complex meaning.
Kubrick does justice to a widely protested war and to the soldiers who fought it. He gives a moral although graphic voice to the soldiers of the era and in my opinion does it most with the surrounding sets. He uses Mise en Scene in a way that I have never seen before. He shows that just by the environment that you can tell the emotions, thoughts, and decisions of a man and much more, a soldier.