Many preachers find a topical approach to preaching to be an easier road. I encourage students not to pursue topical preaching as the primary form of preaching. Why? Because it is harder.
Huh? Easier or harder, make your mind up!
Not all topical sermons are created equal. There is topical preaching that is a short-cut. And there is topical preaching that multiplies the work. What is the difference? Whether or not it is expository topical.
Topical preaching is effectively a form of preaching. It is where the preacher combines passages to make a main point that is their own construct, or the result of a combination of several passages. Expository preaching is not a form, it’s a commitment. It is a commitment to exegete the text so that the text functions as boss of what is said in the message. This can be a single passage exposition. Or it can be a multiple passage topical exposition.
The easy road. I am certainly not suggesting that all non-expository topical sermons are preached because the preacher is lazy. Not at all. But it is an easier approach. You can combine the passages you like, that say what you want to say, without all the baggage of exegesis and contextual analysis. You can tailor the sermon to speak into lives with the real or apparent authority of Scripture, but without the painstaking effort in preparation.
The hard road. The work required to truly get to grips with a passage in order to preach it effectively is significant. Historical, contextual, cultural, grammatical, lexical, and literary study, not to mention textual critical work, original language study, discourse analysis, etc., all add up to a daunting task. Now decide to preach on three passages (perhaps Ephesians 5, 1Corinthians 7 and Song of Songs – for a topical sermon on marriage). Your task is now significantly more daunting. Expository topical preaching is worthwhile, but it is not a short cut.
There is a place and a need for expository topical preaching in the church. Yet for the sake of the preacher, let this not be the staple diet. It is arguable whether there is a place for non-expository topical preaching in the church. But I suggest that for the sake of the listener, let this not be a regular snack, let alone the staple diet.
Biblical Preaching 
I absolutely, wholeheartedly, completely agree. Over the years it has felt like I needed to and should be embarrassed when I do a topical sermon – as if I should apologize for it. But I have always tried to make sure that my approach to topical has been, as you described, expository topical. The goal is to consistently keep the context of a passage in view so that it’s not being used and abused to help me make my point.
This point has also been driven home while serving with a guy that refers to himself as a strictly expository preacher that prefers and usually has one passage each week. Problem though is that expository to him seems to mean that he only uses one passage – and he has been incredibly guilty of twisting and perverting a passage to tie in with the particular topic/series that he’s doing.
Anyway, thanks for addressing this topic.
Beautifully stated. I am a student and I am doing my senior project on varying sermon methods. “Expository topical” is the perfect way to explain this method. Of course, all sermons must rest on good exposition/exegesis. Unfortunately, the topical method has acquired a bad name due to a history of eisegesis. Yet, it is an effective method for addressing certain situations/topics when done right. This is a wonderful explanation. Thank you!