John 1:21 (ESV)
21 And they asked him, “What then? Are you Elijah?” He said, “I am not.” “Are you the Prophet?” And he answered, “No.”
In John 1:21, John the Baptist denies he is Elijah. By this, he was not denying that he was the person referred to as “Elijah” in Malachi 4:5. He only denied that he was literally the historic Elijah, whom the Jews were expecting, whether in resurrected state or in some other unspecified manner.
5 “Behold, I will send you Elijah the prophet before the great and awesome day of the LORD comes.