This section deals with sanctification - the change God makes in our lives when we become Christians. Chapter 6 discusses the continuing struggle believers have with sin.
God forgiveness does not make sin less serious. The availability of God's mercy must not become an excuse for careless living & moral laxness.
In the church in the apostle Paul's day, immersion was the usual form of baptism - that is, new Christians were completely "buried" in water. They understood this form of baptism to symbolize the death & burial of the old way of life. Coming up out of the water symbolized resurrection to new life with Christ.
We can enjoy our new life in Christ because we are united ("planted") with him in his death & resurrection.
The power & penalty of sin died with Christ on the cross. Our "old man," our sinful nature, died once & for all, so we are freed from its power. The "body of sin" is not the human body, but our rebellious sin-loving nature inherited from Adam. The apostle Paul has already stated that through faith in Christ we stand acquitted, "not guilty" before God.
Because of Christ's death & resurrection, his followers need never fear death. This will affect all our activities - work & worship, play & Bible study, quiet times & times caring for others.
We are fully fenced off (because of our union & identification with Christ) from all the old ways of believing & behaving. We have a new start & the Holy Spirit will help us become in our daily experience what Christ has declared us to be.
Reference summary used from the Life Application Bible, KJV, Tyndale House Publishers, Inc., Wheaton, Illinois