The prophet Joel uses the physical and literal to illustrate the figurative and the spiritual.  He 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.

Joel says that the locusts "have laid waste my vines and ruined my fig trees".  Most certainly, locusts did destroy the crops but spiritually speaking, locusts can be symbolic of anything that devours and destroys.  As an example, false teaching will destroy the fruitfulness of God's people.  This passage could be used as a "wake-up call" for the churches today.

Joel 1:12
Surely the joy of mankind is withered away.
During this time, the locusts had destroyed the crops that the people took to the temple for offerings.  Because of this their joy was withered away.  This is an example of the physical affecting the spiritual.  Application for today - joy is diminished because the truth is not preached.  False teaching destroys the joy and fruitfulness of God's people.

Joel calls for the elders in the land to declare a holy fast and cry out to the Lord.  These are God's people he's speaking to, not government officials.

Joel 2:13
Rend your heart and not your garments. Return to the LORD your God, for he is gracious and compassionate, slow to anger and abounding in love, and he relents from sending calamity.

The word "rend" means "to revile" or "enlarge the eyes".  Joel reports that the Lord says not to pretend repentance (rend your garments) but to actually repent (rend your heart).  In other words, He is telling the people to open their eyes to all the evil and actually repent from that evil - don't just give it lip-service.

The next few verses of Joel 2 show a progression they must do in order to receive God's blessings.

1. Repent (rend your heart)

2. Return (to the Lord and His ways, commandments, etc.)

3. Plead (beg His forgiveness)

The great message for us is that no matter what we have done in the past, if we repent, return, and plead, He will relent.

God promises to repay them for the years the locusts have eaten. Again, the same thing applies to all of us today.  He has promised to restore us to a right relationship with Him.  The choice is ours.

"And everyone who calls on the name of the Lord will be saved."
This is a message of hope from the beginning to the end of time.  Those who acknowledge Him as Lord of their lives will have salvation and eternal life with Him.  Again, the choice is ours.

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."

"Multitudes, multitudes in the valley of decision."
We live in the valley of decision.  We must make decisions every day.

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!