Micaiah was a prophet of the LORD at Samaria i.e. in the northern kingdom of "Israel" after Israel had divided into two kingdoms (see The Division Of Israel, The Northern Kingdom and The Southern Kingdom). Although Micaiah is not as well-known as some of the other true prophets, he was no less so than any other because he spoke God's Truth - which is always "first." For that, as has happened to most of God's prophets, Micaiah was not merely unappreciated by the political leaders of his day; he was hated and feared because he spoke the truth, not "politically correct" propaganda - which is almost always Satanic hogwash spewed by ungodly politicians (although most are masters of putting on a fraud show of religious piety).
Micaiah's service to the LORD occurred during the regime of the infamous Ahab and Jezebel:
"16:30 And Ahab the son of Omri did evil in the sight of the LORD [i.e. Christ - see 'Before Abraham Was, I AM' and Christ The Creator] above all that were before him. 16:31 And it came to pass, as if it had been a light thing for him to walk in the sins of Jeroboam the son of Nebat, that he took to wife Jezebel the daughter of Ethbaal king of the Zidonians, and went and served Baal [see also Baal-zebub and Beelzebub], and worshipped him. 16:32 And he reared up an altar for Baal in the house of Baal, which he had built in Samaria. 16:33 And Ahab made a grove [see Groves]; and Ahab did more to provoke the LORD God of Israel to anger than all the kings of Israel that were before him." (1 Kings 16:30-33 KJV)
"Hear thou therefore the word of the LORD"
When King Ahab of Israel (the northern kingdom) again found himself at war with Syria, Jehoshaphat, the king of the southern kingdom of Judah (see also Kings of Israel and Judah), offered to ally the Jews ("Jew" is an abbreviation of Judah) with Israel (sometimes Jews fought with Israel against their common enemies, sometimes they fought against each other - see also Jews At War With Israel), Ahab's false prophets, four hundred of them, proclaimed that Ahab would win against Syria, but Jehoshaphat asked if there were any other prophets available that could be consulted. There was one, Micaiah, but Ahab disliked him because Micaiah told the truth, rather than what Ahab wanted to hear, as did the hundreds of false prophets that infested Israel.
"22:1 And they continued three years without war between Syria and Israel.
22:2 And it came to pass in the third year, that Jehoshaphat the king of Judah came down to the king of Israel.
22:3 And the king of Israel said unto his servants, Know ye that Ramoth in Gilead is ours, and we be still, and take it not out of the hand of the king of Syria?
22:4 And he said unto Jehoshaphat, Wilt thou go with me to battle to Ramothgilead?
And Jehoshaphat said to the king of Israel, I am as thou art, my people as thy people, my horses as thy horses.
22:5 And Jehoshaphat said unto the king of Israel, Inquire, I pray thee, at the word of the LORD to day.
22:6 Then the king of Israel gathered the prophets together, about four hundred men, and said unto them, Shall I go against Ramothgilead to battle, or shall I forbear?
And they said, Go up; for the Lord shall deliver it into the hand of the king.
22:7 And Jehoshaphat said, Is there not here a prophet of the LORD besides, that we might inquire of him?
22:8 And the king of Israel said unto Jehoshaphat, There is yet one man, Micaiah the son of Imlah, by whom we may inquire of the LORD: but I hate him; for he doth not prophesy good concerning me, but evil.
And Jehoshaphat said, Let not the king say so.
22:9 Then the king of Israel called an officer, and said, Hasten hither Micaiah the son of Imlah."(1 Kings 22:1-9 KJV)
Micaiah warned Ahab that his planned military expedition would not be successful. Micaiah also warned Ahab that his other "prophets" were merely political leeches that would tell the king anything that he wanted to hear, even if it resulted in his destruction.
"22:10 And the king of Israel and Jehoshaphat the king of Judah sat each on his throne, having put on their robes, in a void place in the entrance of the gate of Samaria; and all the prophets prophesied before them.
22:11 And Zedekiah the son of Chenaanah made him horns of iron: and he said, Thus saith the LORD, With these shalt thou push the Syrians, until thou have consumed them.
22:12 And all the prophets prophesied so, saying, Go up to Ramothgilead, and prosper: for the LORD shall deliver it into the king's hand."
22:13 And the messenger that was gone to call Micaiah spake unto him, saying, Behold now, the words of the prophets declare good unto the king with one mouth: let thy word, I pray thee, be like the word of one of them, and speak that which is good.
22:14 And Micaiah said, As the LORD liveth, what the LORD saith unto me, that will I speak.
22:15 So he came to the king. And the king said unto him, Micaiah, shall we go against Ramothgilead to battle, or shall we forbear?
And he answered him, Go, and prosper: for the LORD shall deliver it into the hand of the king.
22:16 And the king said unto him, How many times shall I adjure thee that thou tell me nothing but that which is true in the name of the LORD?
22:17 And he said, I saw all Israel scattered upon the hills, as sheep that have not a shepherd: and the LORD said, These have no master: let them return every man to his house in peace.
22:18 And the king of Israel said unto Jehoshaphat, Did I not tell thee that he would prophesy no good concerning me, but evil?
22:19 And he said, Hear thou therefore the word of the LORD: I saw the LORD sitting on his throne, and all the host of heaven standing by him on his right hand and on his left.
22:20 And the LORD said, Who shall persuade Ahab, that he may go up and fall at Ramothgilead?
And one said on this manner, and another said on that manner.
22:21 And there came forth a spirit, and stood before the LORD, and said, I will persuade him.
22:22 And the LORD said unto him, Wherewith? And he said, I will go forth, and I will be a lying spirit in the mouth of all his prophets.
And he said, Thou shalt persuade him, and prevail also: go forth, and do so.
22:23 Now therefore, behold, the LORD hath put a lying spirit in the mouth of all these thy prophets, and the LORD hath spoken evil concerning thee." (1 Kings 22:10-23 KJV)
For speaking the truth, Micaiah was beaten and thrown back into jail to slowly starve to death on a malnutrition diet of bread and water.
"22:24 But Zedekiah the son of Chenaanah went near, and smote Micaiah on the cheek, and said, Which way went the spirit of the LORD from me to speak unto thee?
22:25 And Micaiah said, Behold, thou shalt see in that day, when thou shalt go into an inner chamber to hide thyself.
22:26 And the king of Israel said, Take Micaiah, and carry him back unto Amon the governor of the city, and to Joash the king's son;
22:27 And say, Thus saith the king, Put this fellow in the prison, and feed him with bread of affliction and with water of affliction, until I come in peace.
22:28 And Micaiah said, If thou return at all in peace, the LORD hath not spoken by me. And he said, Hearken, O people, every one of you." (1 Kings 22:24-28 KJV)
Micaiah warned Ahab what would happen, but Ahab refused to heed. It cost Ahab his life.
"22:29 So the king of Israel and Jehoshaphat the king of Judah went up to Ramothgilead.
22:30 And the king of Israel said unto Jehoshaphat, I will disguise myself, and enter into the battle; but put thou on thy robes. And the king of Israel disguised himself, and went into the battle.
22:31 But the king of Syria commanded his thirty and two captains that had rule over his chariots, saying, Fight neither with small nor great, save only with the king of Israel.
22:32 And it came to pass, when the captains of the chariots saw Jehoshaphat, that they said, Surely it is the king of Israel. And they turned aside to fight against him: and Jehoshaphat cried out.
22:33 And it came to pass, when the captains of the chariots perceived that it was not the king of Israel, that they turned back from pursuing him.
22:34 And a certain man drew a bow at a venture, and smote the king of Israel between the joints of the harness: wherefore he said unto the driver of his chariot, Turn thine hand, and carry me out of the host; for I am wounded.
22:35 And the battle increased that day: and the king was stayed up in his chariot against the Syrians, and died at even: and the blood ran out of the wound into the midst of the chariot.
22:36 And there went a proclamation throughout the host about the going down of the sun, saying, Every man to his city, and every man to his own country.
22:37 So the king died, and was brought to Samaria; and they buried the king in Samaria.
22:38 And one washed the chariot in the pool of Samaria; and the dogs licked up his blood; and they washed his armour; according unto the word of the LORD which he spake." (1 Kings 22:29-38 KJV)
Fact Finder: What happened to evil Ahab's wicked wife Jezebel?
See The Fall of Ahab and Jezebel