He shall bruise your head and you shall bruise his heel

Many Christians interpret Gen 3 as follows:

They think the Tempter was originally a bipedal reptile which underwent metamorphosis when God cursed it. They attribute the snake's intelligence, malevolence, and speaking ability to Satanic possession. 

In addition, they think Gen 3:15 is the first messianic prophecy. 

And I will put enmity

Between you and the woman,

And between your seed and her seed;

He shall bruise your head,

And you shall bruise his heel.

There is, however, a problem with combining all these identifications. In the narrative, they think the Tempter is a literal snake or physical reptile. But in the prophecy, they think the adversary is not a literal snake; rather, the adversary is the devil–nothing more and nothing less. 

In other words, they don't think a snake bit Jesus. They don't think Jesus crushed the head of a snake by stomping on it.

So there's a lack of consistency in how they identify the referents. 

A solution is to drop the literal reptilian or serpentine identification and consistently interpret the Tempter in angelic/diabolical terms. On that view, both the narrative and the oracle use serpentine imagery and symbolism. 

Although I often disagree with him, I think Walton is on the right track in this regard:

Serpents are often the object of curses in the ancient world, and the curse in v14 follows somewhat predictable patterns. The Egyptian Pyramid texts (2nd half of the 3rd millennium BC) contain a number of spells against serpents, but they also include spells against other creatures considered dangerous or pests. The serpent enjoys some prominence, however, since it is represented on the crown of the pharaoh. Some spells enjoin the serpent to crawl on  its belly (keep its face on the path). This is in contrast to raising its head up to strike. The serpent on its belly is nonthreatening while the one reared up is protecting or attacking. Treading on a serpent is used in these texts as a means of overcoming or defeating it. This suggests we should not think of the serpent as having previously walked on legs. Instead, the curse combats its aggressive nature.

Likewise, we should not think of the curse of eating dust as a description of the diet of snakes. The depiction of dust or dirt for food is typical of descriptions of the netherworld in ancient literature...These are most likely considered characteristics of the netherworld because they describe the grave. Dust fills the mouth of the corpse...Given this background information, the curse on the serpent can be understood as wishing upon it a status associated with docility (crawling on belly) and death (eating dust). John Walton, Genesis (Zondervan, 2001), 224-25.

This could be deployed to defend a symbolic interpretation, just as the uraeus represented the corbra god of Egypt.