Malachi wrote the words of the Lord to God's chosen people who had gone astray, especially the priests who had turned from the Lord. Priests were not treating the sacrifices they were to make to God seriously. Animals with blemishes were being sacrificed even though the law demanded animals without defect. The men of Judah were dealing with the wives of their youth treacherously and wondering why God would not accept their sacrifices. Also, people were not tithing as they should have been.
But in spite of the people's sin and turning away from God, Malachi reiterates God's love for His people and His promises of a coming Messenger.