As grace and reality (truth) are the basic elements in Eph. 4:17-32, so love and light (vv. 8-9, 13) are the basic elements in the apostle's exhortation in Eph. 5:1-33. Grace is the expression of love, and love is the source of grace. Truth is the revelation of light, and light is the origin of truth. God is love and God is light (1 John 4:8; 1:5). When God is expressed and revealed in the Lord Jesus, His love becomes grace and His light becomes truth. After we have, in the Lord, received God as grace and realized Him as truth, we come to Him and enjoy His love and light. Love and light are deeper than grace and truth. Hence, the apostle first took grace and truth as the basic elements for his exhortation, and then love and light. This implies that he wanted our daily walk to grow deeper, to progress from the outward elements to the inward.
Love is the inner substance of God, whereas light is the expressed element of God. The inward love of God is sensible, and the outward light of God is visible. Our walk in love should be constituted of both the loving substance and the shining element of God. These should be the inner source of our walk. They are deeper than grace and truth.