A simile is a comparison of two unlike things using the words like or as. It is similar to a metaphor, but similes are often considered somewhat less powerful than metaphors. This particular quotation contains a simile, and it compares God's wrath to flood waters that are, for the moment, safely held back by a dam; those waters rise higher and higher, threatening to crest the top of the dam, or even break it, and flood the land around it. In other words, God's wrath builds up, creating more and more pressure, just like the flood waters; one day, finally, it becomes so much that it breaks the figurative dam and spills everywhere. This simile also emphasizes the destructive power of God's wrath and the way it could affect so very many people, just like a flood would.

This is one of the many metaphors that Edwards uses to explain to the audience how God's wrath is ever increasing. Specifically, this metaphor uses a very simple idea that the audience would understand because he wanted to make his point very clear. The metaphor asks the audience to visualize what happens when water is dammed. The water continues to flow from its source toward the dam, but because the dam does not allow the water to move past it, the water will continue to rise behind the dam until either the dam cracks or the water spills over. Either way, the rush of water that will flow from the backed up water will be destructive, and that is the image that Edwards wants to leave with the audience: God's wrath is so great, and it will be destructive if it is unleashed on humanity.