Big Point: In v16-17, Paul has introduced the saving gospel as by Sola Fide, now he begins to explain the urgency of knowing the gospel—because of the wrath of God and three reasons why the wrath of God is righteous/just.

18 For the wrath of God is revealed from heaven against all ungodliness and unrighteousness of men, who by their unrighteousness suppress the truth. 19 For what can be known about God is plain to them, because God has shown it to them. 20 For his invisible attributes, namely, his eternal power and divine nature, have been clearly perceived, ever since the creation of the world, in the things that have been made. So they are without excuse

• God’s Wrath is just because of SIN- people commit ungodly and unrighteous acts.
• God’s Wrath is just because God of the SUFFICIENCY of his revelation- He has given sufficient knowledge of himself to those who commit ungodly and unrighteous acts.
• God’s Wrath is just because when all people SUPPRESS his truth. Suppression of God’s truth is sin against him, and all who suppress his truth are without excuse and under His wrath.