One of the first images that Edwards uses in the sermon is that of a person whose foot slides, causing the person to fall down. This is not only a visual (and perhaps even tactile) image, but it is also a powerful metaphor. He says that people who do not accept God into their lives or remain faithful are taking a similar risk as a person who walks on ice. Just as that person is liable, at some point, to fall down, those individuals who, "notwithstanding all God's wonderful works towards them, [remain] void of counsel, have no understanding in them," take a far worse risk: they are already on the figurative ice and, when God's appointed time comes, he will allow them to be cast down. He will not hold them up from on that figurative ice any longer. Such an image, of being allowed to slip and fall (as one would be cast down into hell) creates a mood of fear. Edwards wants to compel his listeners to change, and fear is a powerful motivator for change.
Soon after, Edwards employs more images designed to create a similar mood. He says,
Though hand join in hand, and vast multitudes of God's enemies combine and associate themselves, they are easily broken in pieces. They are as great heaps of light chaff before the whirlwind; or large quantities of dry stubble before devouring flames. We find it easy to tread on and crush a worm that we see crawling on the earth; so it is easy for us to cut or singe a slender thread that any thing hangs by: thus easy is it for God, when he pleases, to cast his enemies down to hell.
We have an image, first, of those who oppose God being compared, via simile, to dry corn husks or hay being whipped about by the winds or even being quickly consumed by fire. Next, we have the lowly worm or a single thread, coupled with the idea that it is as easy for God to cast one to hell as it is for us to crush that worm or snip that thread. Again, these images create fear in listeners, fear meant to compel them to change their ways.