God wants us to learn to honor our parents because the family is not only the basic building block of society, but also of the Kingdom of God. The godly principles learned and the character built within the human family unit is transferable into the spiritual family relationship of the Kingdom of God. God expects a transference from parents to Him of the character and manner of living derived from keeping this commandment.
Parents are His representatives, His agents, to begin preparations for the Kingdom of God. Thus the creative majesty and power of God is honored and revered in the parents when children obey them.
This passage is directed toward Judah generally and toward the priests specifically at a time when the institution of marriage was under attack. Idolatrous marriages with foreign women were common, as was divorce. Today, marriage is under attack generally, but specifically from perverse same-sex unions. The Jews of Malachi's day wondered why, despite giving their offerings to God, they were receiving no blessings from Him. His answer: their idolatrous marriages and covenant-breaking divorces. He specifically states that a purpose of marriage is that He wants godly children to be produced. These marriages were not producing godly children.
The Hebrew word that is translated as "godly" is elohim, used here as an adjective. It means "filled with reverence and love for God; devout, pious; belonging to or emanating from God." Godliness and holiness are not specifically the same: Godliness is a respectful, reverential attitude, while holiness indicates living as God does. As attributes, as qualities of character, they are absolutely inseparable.
The conclusion is inescapable. After creating Adam and Eve and announcing that He had created them in His image, God immediately establishes the family through marriage. Marriage, therefore, plays an important role in God's overall purpose of creating man in His image. This fact provides the fifth commandment with its greatest degree of significance.