Coppola uses the juxtaposition of contrasting images and themes throughout the film. Probably the best example is when Kilgore obliterates a village and beach so his guys can go surfing. The men are in full combat gear in a cramped helicopter about to rain death on the village, while Kilgore and Lance debate the benefits of heavy vs. light surfboards. While the young soldiers are still cowering in fear and bullets are still flying, Kilgore screams at them to change their clothes and grab their boards.
There are lots of moments like this:
A priest and soldiers kneel at mass while the jungle blows up behind them.
A brightly lit USO stage appears in the middle of nowhere along the dark jungle river.
After a village is bombed, a bunch of U.S. servicemen stand on the back of a truck in the middle of total chaos, shouting things like "We're here to help" at people whose village they just destroyed. It's absurd.
Playboy playmates jump out of helicopters with the Playboy logo on them.
A peaceful family on a small boat gets killed in a spasm of crazy violence.
Lance carries a little puppy inside his shirt during a combat scene.
Mr. Clean gets shot to death as he's listening to an audiotape from home—his mother telling him not to get shot.
Bodies swing from trees as the boat glides peacefully by.
Kurtz recites poetry amid all the horror.
Kurtz's men do graceful tai chi as Kurtz recounts the atrocities he's seen.
These moments of high contrast are part of what gives the film its surreal, hallucinatory quality. By putting all these absurdly contrasting images together—normal life vs. war, light vs. dark—the director's telling us that war is the worst absurdity of all. You can't make sense of it, so don't even try.
In some scenes, like the opening ones, images are even layered on each other, like when the helicopters and jungle intermingle with the image of Willard lying on his bed. We sure know what he's thinking about.