August 21st there will be a total eclipse of the sun across the United States. It's a very rare event.
If you want to teach about it, here are some resources. Lots of additional resources on the NASA site.
Students can read this book on Gif Lingua and study the vocabulary. Or show the book directly in class (teachers can also download books as pptxs).
Gifs are great instructional materials for these kinds of topics!