"The wrath of God is being revealed from heaven against all the godlessness and wickedness of men who suppress the truth by their wickedness" (v. 18).
The Gospel Paul preached is a revelation of the righteousness of God (Romans 1:17). It is a revelation of God Himself, and particularly of His character and justice. Man, made in God's image, lost his conformity to God's character and righteousness when he rebelled against God. When God reveals Himself and His righteousness to a sinful man, that man is destroyed by God's wrath. Now, however, God has revealed His righteousness in such a way that a man may be saved and restored to conformity to God's character and justice. This righteousness, says Paul, is received by faith.
In verse 18, Paul begins to expand on the thought that when God reveals himself to sinners, they feel His wrath. His wrath is manifested against the ungodly because they suppress the truth by their wickedness. Translations vary, and some say that the wicked hold the truth in wickedness. This verb hold means "clasp, seize, possess, hold tightly," and is used positively in places where we are enjoined to hold tightly to the truth of God.
Here the idea is that all men know the truth and they clasp it, but in such a way as to suppress it. Men are not ignorant of God's truth. They know God and they know about His righteous character. They know that they hate Him and reject His righteous character; but in order to reject Him, they must know Him. Paul says in verses 19–20 that they know this because (1) God Himself actively makes it known to them, and (2) the creation clearly reveals Him and His truth.
It is not true that sinners are ignorant of God. Nor is it true that they have forgotten or overlooked Him. It is not true that His revelation is "obscured by sin." Romans 1:20 says that God's righteousness is clearly seen. It says that these are "invisible qualities," which means that all men know things that are invisible, not of this world. It is the goal of all men to suppress this knowledge, however, and that is the purpose of all the religions and philosophies erected by men. They accept some marginal aspects of truth, and absolutize these in order to suppress the most important aspect of truth: God Himself.
Coram Deo
Why do we seek to suppress the truth? Why do we seek to keep God from our thinking? Remember this passage when the secular world seeks the moral high ground in terms of "objectivity" and "open-mindedness." Seek also to see what aspects of God and His law you have tried to suppress.
