Intro. Waffle waffle waffle, essential and potentially key interesting information. Waffle waffle waffle. Facts. Waffle waffle waffle. Build up with more key information. Waffle waffle waffle. Punchline.
A great presentation is better than a shaggy dog story; it should make sense before the punchline. That doesn’t mean you should give everything away in the introduction but if the audience spends most of the presentation unsure of the final point of the whole, much of the preceding information will be lost in processing. This does not mean a detailed list of “key learning points”; “topics to be covered”; or “educational goal” as an introduction. The audience needs to invest in the next few minutes of the presentation and requires more than the existence of the speaker and the ultimate hope of an explanation to do so.
Clearly one should not, nor cannot, give away the whole presentation in the introduction. A challenging question, a stark contradiction of widely held views, a problem or even the punchline without the lead in will force the audience to engage with the presentation at the beginning rather than wait to the end to understand. Even if they don’t agree with your (presumed) point, at least their attention is held. An audience who see no value in a presentation will not engage until that becomes clear. The best presentations do this at the beginning, not with the shaggy dog punchline.