Milkshake (symbol)
That milkshake, of course, refers to the film’s most famous piece of dialogue. When Eli offers to sell the claim to the Bandy land, Daniel tells him that he has already drunk "your milkshake"—meaning he has already extracted all of the oil. Eli’s “milkshake” from which he drinks with his long straw is the oozing pool of crude oil bubbling tantalizingly beneath the land he could not purchase. In that sense, the milkshake may be viewed as a metaphor. In a much larger sense—the sense Daniel is explaining to Eli—the milkshake is a broader symbol of every underhanded dirty deal that businessmen such as himself use to cheat those without the resources to protect what rightfully—if not necessarily legally—belongs to them.
Oil (symbol)
There will be actual blood, but for now oil is its symbolic doppelganger. Just as the circulation of blood maintains life in the human body, oil will become the "lifeblood" of the American economy. Daniel is nothing more nor than less than a vampire, taking oil from whoever he can in whatever way he can using whatever means he can. Oil, in a symbolic sense, becomes the blood that gives life to Daniel; it explains the seeming disappearance of his heart once H.W. goes deaf.
Men dying in the well (motif)
Two men die in oil wells in the film, both towards the beginning of oil extraction and both due to bizarre accidents. Eli interprets the second death as a sign of God’s unhappiness with Daniel’s nonreligious posture. Daniel (and likely the audience) dismisses this, but there is a mystical quality to the motif. We might interpret these deaths as a kind of ‘sacrifice’ made so that the oil can be harvested. In a broader sense, this represents the very real human cost of massive industry. We could also compare these deaths to the near death of Daniel in the opening sequence in the mine. But for luck and sheer determination, Daniel would never have made it out of that situation alive, and now all of his operations seems cursed by the specter of death.
H.W.'s Deafness (symbol)
The bond between Daniel and his adopted son, H.W., is almost certainly there from a narrative point of view to soften Daniel for the audience. Daniel is a man of staggering charisma, but he certainly cannot be termed likable, except for the way he takes on the responsibility of raising H.W. Daniel mostly talks at H.W. rather than listening to him (a pattern that holds in his interactions with most people). When H.W. is deafened, Daniel doesn’t even know how to relate his words to him, let alone understand what H.W. is thinking and feeling. Daniel’s stubborn and unprincipled refusal to learn sign language so he can better communicate with H.W. cements the symbolism. So focused is Daniel on forcing all action and discourse to be on his terms that he ultimately loses his ability to properly communicate with others who will not or cannot engage him on those terms.
Bowling alley (symbol)
Earlier in the film, Daniel states about himself: “I have a competition in me. I want no one else to succeed.” How appropriate, then, that Daniel’s ultimate, final and lasting victory over his nemesis Eli comes via a bowling pin after first hurling bowling balls at Eli as though he were himself nothing but one of those pins to be easily knocked over and cleaned away. The bowling alley is a decadent and worthless space; we have no indication that Daniel enjoys bowling or even games of any kind. We certainly never see him use the bowling alley for its intended purpose. By virtue of being a private two-lane plaything constructed inside his own home, it also becomes representative of the spoils of succeeding at competition. It is an excess of capitalism, and a microcosm of the pointlessness of the ludicrous home Daniel has built for himself.
"Henry Plainview" Music Track (motif)
The same music track can be heard in both the opening sequence of the film and the scene when Daniel buries Henry. The track, composed by Radiohead guitarist Jonny Greenwood, is titled “Henry Plainview” on the original soundtrack. It is comprised of deep, menacing strings layered on top of each other such that the instrumental sounds are barely recognizable. On its own, it is a haunting track and its application is all the more sinister. Both times the track accompanies Daniel digging, both occur deep in the wilderness, and in both instances he is at a low point. In total, the track seems to represent Daniel being isolated and alienated from society. The first case sees him injured and far away from society, facing a long and extremely difficult path to save his own life. The second sees him killing the man he thought was his brother and learning that his real brother was already dead. Daniel’s best chance at true friendship is gone, and we see him drinking and crying over Henry’s diary, wondering what might have been. This track is ghostly, representing things which are out of reach for Daniel, from civilization to his dead brother.
