From http://www.associatedcontent.com/article/37806/a_look_at_sinners_in_the_hands_of_an_pg2.html?cat=38
The Puritans of early America were constantly reminded of the consequences of sinning. One such dynamic pastor of the time was Jonathan Edwards whose mission was to convert and convince his congregation of sinners. He did this through his powerful sermons. In "Sinners in the Hands of an Angry God," Edwards uses several rhetorical devices that contribute to the effectiveness of his sermon.
Edwards uses imagery to paint a horrifying picture of eternal damnation for unsaved souls. His use of graphic words describing the horrors and torment awaiting sinners has a remarkable effect on his audience. Even if Hell isn't a real place and all of the pain and suffering described is a lie, Edwards' way of delivering his message is so successful that it scares his listeners into believing and following his proposed method of redemption.
Elsewhere, he uses imagery to give his congregation a mental picture of God holding sinners above the fiery pits of Hell. After filling their hearts with fear, he uses this image to show them that there is indeed a light at the end of the tunnel in the form of God's mercy and forgiveness. There is no doubt as to the effectiveness of his tactics in using imagery to penetrate into the hearts and minds of those who are present.
Edwards uses figures of speech to compare abstract concepts of God's wrath and the sinner's evil to common experiences. His use of metaphors span over whole paragraphs, such as the one about the bow of God's wrath being drawn and held over the hearts of sinners. This metaphor shows that God could unleash his wrath at any moment but his kindness saves them. Later, Edwards compares sinners to spiders and serpents, creatures despised by humans just as sinners are despised by God. This shows his unconverted congregation how poorly God thinks of them.