Summary: In Galatians 5:1-6, we see Liberty 1) Defined (Galatians 5:1) 2) Defended (Galatians 5:2-4) and 3) Described (Galatians 5:5-6)
In 1963 American civil rights proponent Martin Luther King said: "So let freedom ring. From the prodigious hilltops of New Hampshire, let freedom ring. From the mighty mountains of New York, let freedom ring. From the heightening Alleghenies of Pennsylvania, let freedom ring. But not only that; let freedom ring from Stone Mountain of Georgia. Let freedom ring from every hill and molehill of Mississippi. And when this happens, when we let it ring, we will speed that day when all of God's children, black men and white men, Jews and Gentiles, Protestants and Catholics, will be able to join hands and sing in the words of the old Negro spiritual: Free at last, free at last/Thank God Almighty, we're free at last." http://www.time.com/time/photoessays/mlk/9.html
This is a sentiment that almost everyone desires, but people disagree on the means of obtaining freedom. The Judaizers in Galatia called Christians to return to a way of life under the covenant of Law after they had Christ fulfill that covenant, thereby abandoning the freedom that Christ secured for believers. There is a bondage to law and a bondage to sin—both of which are spoken of in terms of ‘flesh’. Christ sets us free from both, by his cross and by his Spirit. Paul is now moving into dealing primarily with how Christians should live.(Barnes, P. (2006). A Study Commentary on Galatians (p. 221). Darlington, England; Webster, New York: Evangelical Press.)
People define freedom in several ways, some see it in political terms, social, psychological or personal: being left alone by others and not having other people’s values, ideas or styles of life forced upon them. If any of these become the methods of defining freedom, they result in bondage: Bondage to a political system, group or sinful licentiousness. True freedom is liberation from the sins that so easily ensnare us. Jesus Christ is the true liberator and conversion is the act of emancipation to the Christian life of freedom: Freedom from the shackles of sin (Gal. 3:22), works righteousness from the law (Gal. 3:23) and satanic dominion (Gal. 4:3). Christianity not only represents freedom from something, it results in freedom to something: Eternal life, power, protection and hope.
The last verse of Galatians 4 (Gal. 4:31) describes the believer's position-Freedom. This first verse of chapter 5 refers to the believer’s practice-The believer should live as someone who is free. Paul had just finished explaining that the Galatians were not children of Hagar, the slave woman, but sons and daughters of Sarah, born again free by the promise of God. Now that they needed to do was to live free in Christ by the power of the Holy Spirit (Philip Graham Ryken. Galatians: Reformed Expository Commentary. P&R Press. 2005. p. 192).
Galatians 5:1-6 begins the third, and final section of the letter. After defending his apostleship (chaps. 1-2) and his message of justification by faith (chaps. 3-4), Paul now applies that doctrine to practical Christian living (chaps. 5-6), emphasizing that right doctrine should result in right living (ethics). His subject is that sanctification that should result from justification. The life of genuine faith is more than the belief in divine truth; it is also the bearing of divine fruit. In Galatians 5:1-6, we see Liberty 1) Defined (Galatians 5:1) 2) Defended (Galatians 5:2-4) and 3) Described (Galatians 5:5-6)
To live a life free in Christ we must have:
1) Liberty Defined (Galatians 5:1)
Galatians 5:1 [5:1] For freedom Christ has set us free; stand firm therefore, and do not submit again to a yoke of slavery. (ESV)
Throughout the scriptures, including here, the author often links facts with appropriate actions. They link an indicative (what God has done) followed by an imperative (what we should do in response). Since Christ has set us free, from Jewish ceremonial laws and regulations (cf. Gal. 2:11–12) but not from obedience to God’s moral standards (Gal. 5:14–6:1) we must stand firm in that freedom. This freedom, as the whole Epistle and this context make plain, is not primarily a freedom from sin, but rather from the law (as a means of salvation) (Stott, J. R. W. (1986). The message of Galatians: Only one way (p. 132). Leicester, England; Downer’s Grove, IL: InterVarsity Press.).
Please turn to Romans 6
In light of what Paul has been saying throughout the letter, he also here implies a disturbing question: "Why, then, do some of you want to go back to being like Ishmael, who was a slave, an outcast, and separated from God?" It makes no sense at all.
Paul exclaimed to the Roman church:
Romans 6:17-19  But thanks be to God, that you who were once slaves of sin have become obedient from the heart to the standard of teaching to which you were committed, and, having been set free from sin, have become slaves of righteousness. I am speaking in human terms, because of your natural limitations. For just as you once presented your members as slaves to impurity and to lawlessness leading to more lawlessness, so now present your members as slaves to righteousness leading to sanctification. (ESV)