There are many sources of video material for teaching STEM topics. Here are four examples.
Teaching Channel is a video showcase of inspiring and effective teaching practices in American schools. The video library offers a selection to support many subject areas. The videos support alignment with Common Core State Standards and offer supporting materials for teachers.
Here is one example from a query for STEM materials.
The Khan Academy video collection covers K-12 math, science topics such as biology, chemistry, and physics, and even reaches a little bit into the humanities with playlists on finance and history. Each video is a digestible chunk, approximately 10 minutes long, and especially purposed for viewing on the computer. You can browse these resources for a brief time, but to gain full access, you will need to set up a free account.
Here is an example from the collection "Life on Earth and in the Universe", about Firestick Farming by aboriginal Australians.
Spangler Science is a YouTube Channel that is full of videos of fun science experiments using everyday objects and materials. Use it as a lead-in for a serious discussion of scientific principles.
Here's one example. Did you know that some (but not all) pop cans float in water? Follow this link to find out why.