Chapter 4

Opens like this:

1 "For behold, the day is coming, burning like an oven, when all the arrogant and all evildoers will be stubble. The day that is coming shall set them ablaze, says the LORD of hosts, so that it will leave them neither root nor branch. [Mal 4:1 ESV]

Not much beating around the bush and hand holding here.  On some future day, it will be too late to choose rightly.  On that day, the evil get run over by the good.  Justice, righteousness, fairness...all these will win on that day.  The book ends, the OT ends, with these verses:

5 "Behold, I will send you Elijah the prophet before the great and awesome day of the LORD comes. 6 And he will turn the hearts of fathers to their children and the hearts of children to their fathers, lest I come and strike the land with a decree of utter destruction." [Mal 4:5-6 ESV]

And the NT is going to open with the appearance of Elijah.  Just as promised at the end of Malachi, the last OT prophet for over 400 years.