For the members of the platoon, reality is difficult to process.
How does one, for example, make sense of guys rationalizing killing each other, or of death and destruction that surrounds them? How does one think of the jungle as anything other than a "beast" (King), waiting to devour the soldiers? The soldiers in Platoon repeatedly resort to metaphors to describe their experiences, to explain things that are too horrific for normal explanations. The characters always describe the "reality" of war as something other than a reality where the horrors of Vietnam are unthinkable and where genuine morality exists. For the soldiers of the platoon, the jungle is a beast, a tropical hell; Barnes is a supernatural, god-like immortal; Elias a prophetic, Christ-like figure. There is no absolute reality. It's different for each soldier.
Questions About Versions of Reality
Why do the soldiers resort to metaphors (the jungle and the enemy it contains are a "beast") to process their reality? Is this a defense mechanism?
What does Barnes mean when he says "I am reality"? What reality does he represent?
For Bunny, Vietnam is a grown-up's playground, a place where the only worry is death. How does this reality square with that of the other soldiers? Is it a realistic way to look at things?
What is Elias' version of reality? Taylor's? How are they related?
Chew on This
There's no such thing as a reality. Everybody processes things in a different way, which means reality is different for everybody.
While every soldier has their own version of reality, Platoon ultimately shows us that the reality of Vietnam was the reality of horror—man's inhumanity to man.