One of the best CppCon talks (from 2014, so it predates concepts, but still of very high quality and extremely relevant) that helps you get started with template meta-programming:

• part 1: https://www.youtube.com/watch?v=Am2is2QCvxY
• part 2: https://www.youtube.com/watch?v=a0FliKwcwXE

TMP is a really beautiful part of C++ once you get the hang of it.