There are few details recorded about the Prophet Malachi.
We do know that he was a part of the Anshei Knesset Hagedolah, the Great Assembly that met in the Holy Temple in Jerusalem at the beginning of the Second Temple era.
We also know that he was one of the last three prophets to be included in the era of prophets. The other two were Hagai and Zechariah. The Biblical commentator, Rabbi Avraham Ibn Ezra (1089(?)-1164), says that it was because there would be no prophets after him that Malachi told the Jews (3:22), “Keep in remembrance the teaching of Moses, My servant.”
The prophetic writings close with one of Malachi’s more well-known prophecies that Elijah the prophet will herald the messianic era (3:23): “Lo, I will send you Elijah the prophet before the coming of the great and awesome day of the L‑rd.”
There is a minority opinion in the Talmud that says that Malachi was actually Ezra the Scribe. There is another opinion that he was Mordechai from the story of the holiday of Purim. However, the opinion of the majority of the sages in the Talmud is that Malachi was a separate individual.