Romans 1:18 — For the wrath of God is revealed from heaven against all ungodliness and unrighteousness of men, who hold the truth in unrighteousness.
Revealed — present tense. The revelation of wrath is ongoing. The expression of that wrath is yet to come (at the end of the Tribulation and at the end of the Millennium). The wrath of God is revealed by the gospel. It is against all and any sin.
Ungodliness = our sin against God, disregard of God's existence
Unrighteousness = our sin against each other (immorality), not being right with God.
The ungodly live as if there is no God. The unrighteous live as if the will of God doesn't matter.
Hold = keep back, suppress. Men have had the truth revealed to them but deliberately suppress it.