There are many things that we as worship leaders consider when building our set list from week to week. Of course, we should be praying about it first and foremost! After that, there are many things to consider as we strive to put together something that will be effective in the worship service. As the worship portion of the service should connect as much as possible with the other aspects of the service... and as we should be setting the stage for what the pastor will be sharing to follow... the consideration of the sermon topic or overall theme of the service should be part of your planning process.
As a worship leader, I have worked with a couple of lead pastors that wanted the worship set to follow the theme of the message. Thankfully, neither were overly hard-core about it. I did learn through experience that having at least some of the worship set directly tieing in to the following sermon was helpful for the overall flow and effectiveness of the ministry taking place. At the same time, you shouldn't use a song based only on the theme / topic of the song if you are forcing it into place. That doesn't help anyone or anything.
So, while viewing this subject matter and attempting to build a theme-focused worship set, here are some considerations:
1) Always remember, not EVERY song in the set needs to follow the theme completely. Sometimes simply just ending the set with a song that can easily be flowed out of into the message works very well. Throughout the set, you should have a consistent flow from one song to the next. The theme / text / lyrics of each song doesn't have to line up completely for songs to work together. There is much more to the overall flow than just text.
2) You must be careful to not force a song into the mix just because it fits the targetted theme. Just because the lyrics coincide with the message does NOT mean that the song will work in that particular set or service! This is the same issue as when some worship leaders force an old "standard" or "hymn" into the set just to fulfill a quota or please certain groups or individuals in their congregation, regardless of if the song really fits or works within that set. It's more important that the worship set flow and effectively lead the congregation into God's presence than it is to sing a specific theme in every song. If the worship set is effective, the congregation will be ready and the worship team will have done their job... regardless of any theme or lack thereof.
3) Remember who is in charge! In most cases, you as the worship leader are not the final authority in your church. You work with and under a lead/senior pastor... and that person is the one in authority that you must be submissive to. If your pastor tells you (or requests) that you include a particular song in your set, likely due to his/her message topic, then you need to include it. If you have a real issue with it (beyond your personal preference), then you of course can have a discussion with your pastor about it. You should always be striving to be on the same page with your pastor and church leadership. In the meantime, just include the requested song. Even if you know it's not going to work well, give it your best shot and your biggest effort to make it work as best as possible within the rest of your set.
4) Utilize resources to find songs for your target theme, or even discover new songs that you should learn and introduce at your church. Here on WorshipReady.com, each song page has a list of theme tags that relate to that song. You can click on any of those themes to get a list of other songs that are tagged with the same theme. I often use this myself to help hone in on potential songs that incorporate a particular topic or theme. In doing so, I always have moments of "oh, I forgot about that song!" as well as gaining an awareness of new songs that I can then check out as possible songs to add to my bag of song options!
So, can a themed worship set work? Absolutely! Is it a good idea? Sure! Just be careful not to force anything. If it's not working or doesn't feel right, then change it up! You should always be aware from week to week what is and is not working in your worship services... and make adjustments as necessary. When done right, a themed worship set can be very effective. Hopefully these thoughts can help you in your set building process!