"Eraserhead" by David Lynch is a tough one to wrap your head around. It's a feature length experimental film that seems to be influenced by such luminaries as Maya Daren and Stan Brakhage.
The best way into this film for me is to use the Fruedian metaphor of the cave. To better explain this theory I'm going to quote Howard M. Gluss, Ph.D. :
"Outside the cave is the conscious mind. This is the realm of everyday consciousness and thoughts-where everything, seemingly, is relatively accesible to constant awareness. When you first enter the cave, you encounter the preconscious mind-the part of the mind where thoughts are below the surface of immediate awareness-yet with little trouble the individual can access them. But deep within the cave lies the unconscious mind, the region of our soul that harbors thoughts that are unacceptable or incomprehensible to the individual. These thoughts are not easily brought into awareness...The banishment to the dark recesses of the back of the cave of these highly troubling or inappropriate feelings can prove a tremendous battle. When a character has a great deal of repressed material, the battle to keep those terrible things safely hidden and cordoned off with defense mechanisms can lead to complex, irrational, and even seemingly insane behaviors."
There are many dark chambers in the mind of the protagonist in "Eraserhead" and many disturbing images of sexuality, motherhood and parenting. And if you're a David Lynch fan you probably wouldn't have it any other way.