Videos can enliven a presentation. They can be used to illustrate something that would be hard or impossible to recreate on stage or with static slides. So there's nothing wrong with showing a video, presuming it is short.
But how long is "short"? Think back to the last time you watched a video in someone's presentation. 30 seconds are fine. One minute, however, can already feel long. Get to 3 minutes and all you want is for the video to end.
Why is that so? Why can't we bear to watch a 5-minute video but sit through entire movies which are 90 minutes or longer?
One of the reasons has to do with our expectation: We came to see a talk, not for a movie. We want to hear directly from the person up on the stage. We don't want to watch pre-recorded content; we could just as easily have done that at home and spared us the trouble of coming to the venue. The live experience is important to us and we feel cheated when we get less of that stage time than we expected.
Another reason is of course the different purpose: We go to the cinema to spend an evening, possibly with friends and family, to be entertained. Even if we came to watch a documentary, we expect the movie to be well-made, engaging, and a self-contained experience. Add any hassles, minor as they may be, and the audience rather stays at home, watching a bootlegged copy or doing something else entirely. Cinemas try to make watching a movie a positive experience, using the latest technology in projection and sound, offering comfy seats, and selling you something to eat. So even if you came to learn something, it's an entirely different experience from attending a presentation.
So, other than picking short and relevant video clips, what else can you do so that videos in your presentation feel less awkward?
Don't mention the mechanics. Don't say "and now I'm going to show you a video". Instead, mention the purpose or open with a question. "But how does photosynthesis work on a cellular level? Let's have a look." And without further ado, you show the video. (That's a fictitious example, btw. I have no idea if you can actually film a cell doing photosynthesis; but I'd like to see it if it was possible!)
Embed videos. You've all seen presenters drop out of the presentation, switch to the desktop, search for the video, double-click on it (several times, since it doesn't work on the first try), maximise the video, adjust the sound, move the mouse cursor out of the way (hopefully) - and then they have to switch back to the presentation software when they're done. It's just killing the flow and any suspense you may have been able to build up to this point. Modern computers and presentation software can easily cope with presentations a few 100 MB in size. Embed the video in the slide, enable autoplay, and test it - both the technical side (Does it play? Is the sound on?) and how you would lead up to the video in your narration.
Test it. Not only should you test the presentation with the embedded video, but you also need to test things at the venue, before your talk. Is the computer connected to the sound system? How loud is it? If it's not your own computer: Does it still work? Is there maybe a delay when it loads and you make the switch to the slide with the video on? If so, adjust your buildup.
Rule of thumb: The video should come up just as naturally as any other (static) slide in your presentation. Only then can it have the full intended impact.
(Graphic by OpenClipart-Vectors, from pixabay, CC0)
Please email me for details.