The sermon famously horrified and persuaded listeners—afterwards, they eagerly sought to repent of their sins and convert in order to avoid the divine wrath Edwards had described. The mood the sermon provokes is one of extreme fear and contrition.
It might go without saying, but this most famous of all "fire and brimstone" sermons has primarily a fearful, anguished mood. Edwards's descriptive hellish metaphors, as well as his well-constructed argument that everyone who does not believe in Jesus will go to hell, frightened his audience into converting when they had earlier been unwilling. Because listeners would have seen Edwards as an authority, and the Bible which he quoted as an even greater authority, they had serious reason to worry about their future place in hell if they were convinced by this sermon's logic. Edwards urges his listeners to repent and come to Christ in order to assuage the fear he has provoked in them.
After being convinced that they were going to hell, the audience would likely have been hopeless. But Edwards makes sure his listeners have reason to hope—if they do what he says, that is. By describing the believers who will be saved, Edwards adds hope to his sermon. He nevertheless maintains the fear he created earlier by describing the saved individuals as "many others," and by continuing to refer directly to the audience as sinners. If the audience wants to capitalize on the hopeful mood Edwards has expressed, they have to convert first. Although listeners might have been scared after Edwards preached, they also would have left the sermon believing they could avoid hell if they repented and were saved.
Both fear and hope might have prodded listeners to convert, but it's also possible their own guilt convinced them. Even the vengeful God of Edwards's sermon is described as just and fair: he gives people an opportunity to do right, he restrains his wrath for long enough that they might, and he only does "what strict justice requires." Jesus, who wants to help sinners and welcomes them into his protection and comfort with open arms, is likewise a highly sympathetic figure in the sermon. On the other hand, sinners themselves are described as deluded, foolish, and conceited. Listeners might have recognized themselves in Edwards's description and felt guilt for their failure to accept Jesus's sacrifice or take advantage of God's grace.