What is the meaning of Malachi 3 chapter verse 1-4?

There was never a person called Malachi. The Book of Malachi was written anonymously. probably in the early post-exilic period. Verses 3:1-4 refer to 'my messenger' (Hebrew: mal'aki) and it is this reference that gives the book its name: Malachi.

The author says that God had promised to send a messenger - and here I am. But who will be with me when I purify the sons of Levi (the priests)? Verse 4 is an oracle of good fortune because the messenger has come.

The author then goes on, making a bitter attack on the reigning Temple priesthood, the sons of Levi, whom he opposes.

However, there is another way of reading this, recognised by many Christians. There are just enough parallels that it can be said to be a prophecy of John the Baptist. Burton L Mack (Who Wrote the New Testament) calls this a trick because, with a little ingenuity, one can demonstrate whatever prophecies one wishes in The Bible.