The prophet Joel uses locusts as a foretaste of God’s judgment to come. Joel looks back on what the locusts have done and looks forward to what the consuming fire will do during the wrath of God on the Day of the Lord. The book of Joel is a perfect example of foreshadowing and also a perfect example of the use of both figurative and literal…literal – the actual locust infestation and figurative – the fire and the wrath of God that will come and consume as the locusts had done. The analogy of the locusts and the wrath of God is spelled out in Joel 2:25.

Note the similarities in the following passage in Joel and the passage in Revelation. They both speak of the wrath of God on the Day of the Lord.
Joel 3:13
Swing the sickle, for the harvest is ripe. Come, trample the grapes, for the winepress is full and the vats overflow-- so great is their wickedness!'

Rev 14:15
Then another angel came out of the temple and called in a loud voice to him who was sitting on the cloud, "Take your sickle and reap, because the time to reap has come, for the harvest of the earth is ripe."

Joel also tells us that the day of the Lord is near, as do so many of the prophecies concerning the last days, which is why we named the book THESE Last Days. 

Joel also tells of Armageddon, the gathering of the nations, their restoration and the beginning of the millennium. 

Read the section labeled Day of the Lord (Ch. 2) as if it were the army of the Lord.

Joel 2:32a
And everyone who calls on the name of the LORD will be saved;

Our ever loving God offers chance after chance after chance for salvation, even on the Day of the Lord He still holds out His hand, waiting for people to acknowledge Him as Savior and Lord. What patience! What grace! What love!