This may somewhat depend on the field and maybe I am a bit biased, but I have not seen a single overview slide (following the title) that was not a total waste of time so far. Eloquent Science agrees with me.
Essentially, there are two flavours of useless overview slides:
The overview slide and what the speaker says alongside it tell me that the talk has a more or less standard structure. To give an extreme example:
First, I will give an overview; then I will present my methods; then I will present my results; finally, I will draw my conclusions and give an outlook.
Nothing of the above helps anybody to follow the talk better or in any other way, as they already expect something along the lines of this to happen. If there are deviations in the detail, this is nothing they need to know at this point of your talk. Even, if your talk has some very unorthodox structure, e.g., if you start with the results and then have the methods follow, you can mention this when you start describing the results and do not need an overview slide for this.
The overview slide and the speaker tell me something about the actual content, such as
I first introduce the problem of banana transmogrification. Then I explain our latest progress on flux compensators. Finally, we will report on our results on transmogrifying bananas with flux compensators.
The problem here is that most people attending the talk know next to nothing about flux compensators or banana transmogrification and thus will have forgotten that flux compensators are going to appear in this talk halfway through your first slide on bananas. Sure, there will be one or two people in the room who read your recent paper on apple transmogrifications with flux compensators, but those are not the people who need your didactic attention – they would probably even understand the talk if you went through the slides backwards.
This does not mean that you shouldn’t explain that the reason why you are talking about flux compensators is that you want to use them for banana transmogrification, but that’s something you should do when you transition from banana transmogrification to flux compensators. In general, you have to remind the audience again and again why you are doing things, explain connections to what you have said before and guide them through your talk with this, but that’s something that happens during the talk, not in the beginning.
As already said, this may be somewhat field-dependent. So, you are probably best advised to think about what you are going to present on this overview slide and take the point of view of the audience to consider whether it really needs and understands this information at this point of the talk and is not better said later in a more fitting context.
Also, there are a few occasions where some general sort of overview slide can be a good idea. For example:
In a long talk that is separated into several large and seemingly unrelated chapters, you might give a brief overview after the introduction to the general topic.
If you address several aspects of something that are at first separate. For example, a colleague of mine once gave a talk where he “took a tour through the parameter space” of a system and regularly showed an overview diagram of the parameter space like a tour map, indicating what places were already visited and what came next.
If the answer is no, how do I transition smoothly from the Paper Title Slide to the one on Motivation for the talk (For example : Why I love Science?).
How would the transition from an overview slide to a motivation be more smooth than from a title slide to a motivation?
That being said, I do not think that this transition needs to be smooth at all. The transition from whatever happened before you started talking to you talking is very unsmooth already, and thus it won’t be any worse if you dive straight into the big important reason why you are doing what you do.
However, often something relevant to your motivation appears in your title and you can build a transition on this. For example:
As you probably guessed already, I spent some time on transmogrifying bananas and you probably wondered why anybody would want to transmogrify fruit in the first place.
(I intentionally ignored your example topic, as in this case the whole talk would be a motivation.)