In chapter 5, Paul addresses many moral and ethical issues along with the proper ordering of relationships both in the church and in families. The whole of Paul’s counsel seems wrapped up in this, that we are new creatures in Christ; therefore, we are to look different than the world. We are to look like Christ.
Into chapter 6, Paul continues to give counsel about relationships – parents and children & servants and masters – but most people, I suppose think of chapter 6 in terms of Paul’s instructions regarding spiritual warfare. He reminds us that, ultimately, our battle is a spiritual battle. In the battle, we have this assurance, wherever we find ourselves, if we rest in the Lord and put on the whole armor of God, that we will have the victory, whatever Satan uses against us. After all, the One who is in us is greater than he who is in the world (1 John 4:4)!
Stand up, my soul; shake off your fears,
and gird the gospel armor on;
march to the gates of endless joy,
where your great Captain Savior's gone.
Hell and your sins resist your course;
but hell and sin are vanquished foes:
your Jesus nailed them to the cross,
and sang the triumph when he rose. –Isaac Watts (1707)