The devil ... has nothing to do with the truth, because there is no truth in him. When he lies, he speaks out of his own character, for he is a liar and the father of lies. (John 8)
I am ... the truth. (John 14)
What is the goal of preaching? A primary goal is to expose lies. Satan is the father of lies and he has been rather successful in persuading folk to accept his lies as true. This is why so many lives are so broken. Preaching needs to show the people these lies and the terrible results of believing them.
The companion to this aspect of preaching is to point to the truth. This is more than stating propositions that are accurate. Jesus is the truth. So, preaching truth is about showing the people how he makes life work the way that it is supposed to work.
So, from this point of view the goal of preaching is freedom, freedom from lies so that we can live well. This is a slow process because the lies have gone deep and feel so true. And Satan doesn't just sit around. Preaching is Spiritul warfare.
An unpolished thought