It is a fascinating passage.
Matthew 17:
12 But I say unto you, That Elias is come already, and they knew him not, but have done unto him whatsoever they listed. Likewise shall also the Son of man suffer of them.
13 Then the disciples understood that he spake unto them of John the Baptist.
Related I can get lost (timewise) pondering Melchizedek (The King of Salem).
There's a section in Seder Olam that speaks for early prophets (and prophetesses), mentioning Adam and Seth - when mentioning Seth, Psalm 110 is quoted, "priest forever of the order of Melchizedek". There was an ancient thought that Seth was that "King of Salem" and that he shadowed or mirrored an Heavenly priesthood that existed long before the Levites or Moses or the Temple. Later the "order of Melchizedek" is quoted in the NT book of Hebrew, referring to the unending priesthood in Heaven, of whom Yeshua is the forever priest of that Priestly Order.