“Man of God” is the description given to a man that follows God in every way, who obeys His commands with joy, who does not live for the things of this life but for the things of eternity, who willingly serves his God in giving freely of all his resources yet gladly suffers as a consequence of his faith. Perhaps Micah 6:8 sums up the man of God in one neat verse: “He has showed you, O man, what is good. And what does the Lord require of you? To act justly and to love mercy and to walk humbly with your God.”
The man of God does not swindle or defraud his employer by turning up late for work or spending an hour on the internet during work hours; he doesn’t gossip or slander; he keeps his mind and heart pure by guarding his eyes and ears from the filth of the world; he is the spiritual leader of his family. He does everything opposite to what the world does or approves of; he goes "against the grain" of society because he knows these things displease God; he considers those who are "disadvantaged" or those rejected by society, those who are lonely or despairing; he is a listener to other people’s problems and does not judge.
Most of all, the man of God understands that when our Lord commanded him to "be perfect, therefore, as your heavenly Father is perfect" (Matthew 5:48), he is only able to accomplish that because God enables him to be “holy and blameless in his sight” (Ephesians 1:4) through His power and the indwelling of His Spirit. On our own, we are incapable of holiness and perfection, but through Christ who strengthens us, we can "do all things" (Philippians 4:13). The man of God knows that his new nature is that of the righteousness of Christ which was exchanged for our sinful nature at the cross (2 Corinthians 5:17; Philippians 3:9). The final result is that he walks humbly with his God, knowing that he must rely solely upon Him to be able to live to the full and persevere to the end.
Perhaps the Christian today is lacking in these qualities, but this is what simple religion is all about—the simple religion that is yet sufficient to please God: helping those in distress and keeping oneself from being polluted by the world (James 1:23). We can have an awareness of all biblical doctrines, we can know all the theological terms, we may be able to translate the Bible from the original Greek and so on, but the principle of Micah 6:8 is the principle that the man of God must follow: act justly, love mercy, and walk humbly with God.