When we talk about expository speaking, we are talking about the kind of speaking in which the speaker selects a particular text of Scripture. He explains it in the context of the day in which it was written. He then applies it to the day in which the listener is living.
This kind of preaching is not the norm; it’s the exception. “Springboard preaching” is far more common.
That is, the speaker reads the text and then springboards from it to say anything he cares to say. It has been said that some people use the text like the national anthem at a football game. It gets things started, but then it’s never heard from again.
R. Larry Moyer, Show Me How to Preach Evangelistic Sermons, Show Me How Series (Grand Rapids, MI: Kregel Academic & Professional, 2012), 30.