Haggai, Zechariah, & Malachi
Haggai
Haggai prophesied in 520 BCE, encouraging the Jews to get busy building the Temple.
He told people that they had rebuilt their own homes, but had left the LORD without a house of his own. They were struggling to survive. Haggai told them that they would need to rebuild the Temple if they expected to receive the LORD's blessing.
Haggai promised the Jews that the Temple they would build would be greater than Solomon's.
He repeats the promise that if they do build the Temple, the LORD will bless them.
Zechariah
The book of Zechariah falls into 2 parts. Chapters 1-8 which talk about rebuilding the Temple and chapters 9-14 presume a completed second Temple.
Chapters 1-8 date from 520-518 BCE. This section is comprised mainly of 8 visions:
1. The four horsemen
2. The four horns and the four smiths
3. The man with the measuring line
4. The accuser and Joshua
5. The gold lamp stand and the two olive trees
6. The flying scroll
7. The woman in an ephah
8. The four chariots
Chapters 9-14 probably were written later, before 333 BC when Tyre fell to Alexander. These chapters make no mention of Zechariah himself, and make references to the Greeks so scholars think that these chapters were a later addition to the original 8 chapter book.
The major theme of the second half of Zechariah is the day of the LORD and the ultimate triumph of Jerusalem against its enemies.
Malachi
Malachi is the last book of the Old Testament in Christian Bibles. The book does not give a set historical date or any information about the author. Malachi literally means "my messenger" so like Obadiah, this name may be a title instead of the name of the prophet.
The themes of the book suggest that Malachi was active around the time of Ezra and Nehemiah when the Jews had become disillusioned and careless with their worship. The book takes the form of a dialogue between the LORD and the people.