Paul found himself writing to a society in Ephesus that was, oddly enough, not that much different to our current day's; it was a moral and ethical cesspool, and they, like us, needed a rewiring of imaginations.
Ephesians 5 is a call to real discipleship. The basic starting place is a change in our behavior.
If you're a Christian, then act like it!
Our tongues will be tamed, our drinking will not go to excess, our greed will be checked, our sex will be reserved for marriage, etc.
We want to clean up our act and imitate God, which we do, by looking to Jesus. The Christian life is measured in light. Our manner needs to be that of our our master and the Hopy Spirit will help us.