Malachi 1:1 The burden of the word of the Lord to Israel by Malachi.
Malachi is the last book before Matthew.
I was raised with the Old Testament and the New. It was many years ago the Lord showed me how the enemy had used that and we should have always see the Scriptures as 1 Book, 1 Story. Malachi is a warning and a promise. The 400 years between Malachi and Matthew , the 2000 plus years since the Cross , shows us God's time is not like ours.

Everything we have read up to this chapter shows us why we needed Jesus. God was tired of empty sacrifices... We can see many of the things that where promised happened and we can count on the ones to come.

Malachi 3:6 For I am the Lord , I change not; therefore ye sons of Jacob are not consumed.

God is tired of empty sacrifices ,bad priest and a people that have robbed Him in the chapter . I find it amazing knowing what we have done in 100 years , that in Matthew and on they knew Scriptures like they did.
We know Peter knows Malachi 4. Many things in the chapters ahead happened and are happening. We see the pattern that led God to flood during the time of Noah . We see the pattern that led God to destroy Sodom. We see earth and the people will repeat those patterns and leads God to fulfill Malachi 4 and 2 Peter 3.
In Malachi they could not see they had left God and where robbing Him and we are told the end days will be the same. They where acting out like they loved God but He saw their hearts , He sees our as well.
Malachi 3:16 Then they that feared the Lord spake often one to another: and the Lord hearkened, and heard it, and a book of remembrance was written before him for them that feared the Lord , and that thought upon his name.

This life is all about getting our name in the Book of Life , Loving our Creator and understanding the Sacrifice that was made because of His love for us...This world has an expiration date and Malachi 4 tells us ,,, For, behold, the day cometh, that shall burn as an oven; and all the proud, yea, and all that do wickedly, shall be stubble: and the day that cometh shall burn them up, saith the Lord of hosts, that it shall leave them neither root nor branch . 2 Peter 3 tells us the same , so no matter what today holds , know the One that holds it.