We learn something about Paul's life in this epistle not reported elsewhere in the New Testament (e.g. 1:17-24). We also see how the Galatia churches faced a challenge to the gospel. The principles in these chapters are relevant for all time.
Galatians 1:17–24 (NIV)
I did not go up to Jerusalem to see those who were apostles before I was, but I went into Arabia. Later I returned to Damascus. Then after three years, I went up to Jerusalem to get acquainted with Cephas and stayed with him fifteen days. I saw none of the other apostles—only James, the Lord’s brother. I assure you before God that what I am writing you is no lie. Then I went to Syria and Cilicia. I was personally unknown to the churches of Judea that are in Christ. They only heard the report: “The man who formerly persecuted us is now preaching the faith he once tried to destroy.” And they praised God because of me.
Even in the earliest days of Christianity, false teaching was apparent. Paul didn't over look it, pretending it did not exist; neither did he minimize it, saying it doesn't matter.
The Judaizers were teaching that a Gentile had to undergo circumcision, becoming a Jew before he could be a Christian. This was not the gospel that Paul and his colleagues had preached, it had become a perverted version of the gospel.
The truth, as he explained later (2:15-21), is that all people - Jews or Gentiles - are saved by faith in Christ, not by obeying the Mosaic law.
Paul's message was revealed by Jesus. In these autobiographical lines, the apostle explains that the source of his gospel was not from any man, but direct revelation from the Christ whom he met on the road to Damascus (see Acts 22:1-16).
Paul's message was confirmed by the apostles (2:1-10) as they accepted Paul and encouraged him in his ministry to the Gentiles.
The gospel needs to be defended (2:11-16). Paul confronted even his close friends Peter and Barnabas when they were in error. The gospel demands that all people bring their doctrine into harmony with it, regardless of popular opinion.
The gospel needs to be demonstrated (2:17-21). Godly living is the mark of a believer. Galatians 2:20 provides a wonderful goal for each Christian. The attacks of the ungodly are silenced by righteous living (1 Peter 2:15).
I have been crucified with Christ and I no longer live, but Christ lives in me. The life I now live in the body, I live by faith in the Son of God, who loved me and gave himself for me.
For it is God’s will that by doing good you should silence the ignorant talk of foolish people. Live as free people, but do not use your freedom as a cover-up for evil; live as God’s slaves. Show proper respect to everyone, love the family of believers, fear God, honor the emperor.