How does the Melchizedek priesthood relate to a high priest for Gentiles?

Les teaches that Melchizedek was simply Jehovah, or God the Son, in a theophany—God appearing in human form to Abraham. This role, he explains, would define the whole New Testament economy: Gentiles have to have a high priest who is not tied to the law of Israel. Since Melchizedek had no genealogy, no beginning or ending, Les feels this was Christ appearing to Abraham in human form to lay the groundwork for our high priest as Gentiles. He contrasts this with the Levitical priesthood: beginning with Aaron, Israel’s first high priest, every priest had to come from the tribe of Levi, so that law-bound priesthood could not provide the Gentile high priest.