The Bible Project offers handy videos that explore Bible content.

Here are links to their videos of summaries of each of the early epistles:

Video Summary of the Book of Galatians

Video Summary of the Book of James

Video Summary of the Book of 1 Corinthians

Video Summary of the Book of 2 Corinthians

Video Summary of the Book of 1 Thessalonians

Video Summary of the Book of 2 Thessalonians

Bonus Video:

Overview of the Old Testament in 8 minutes