Romans 1:16–17 is often used as the key verses to summarize the book of Romans. Paul declares boldly why he is not ashamed of the gospel about Jesus that he preaches around the world. This message is nothing less than the power of God for everyone who believes, both Jews and Gentiles. It is about being declared righteous by God because of our faith in Him.
For a more detailed summary select the link below.
“Romans 1:16” Bibleref.com
16 For I am not ashamed of the Good News of Christ, because it is the power of God for salvation for everyone who believes, for the Jew first, and also for the Greek.