Who is “The (Arch)angel of the Lord”?

Thus Clement of Rome taught around A.D. 90f that Malachi’s Angel of the Covenant is the Lord Jesus Christ (First Epistle to the Corinthians, ch. 23).   So too Matheetees, in his A.D. 130 Epistle to Diognetus (ch. 7).

Around that same time, the Shepherd of Hermas in his work The Pastor, wrote (III:8:3): "The Law of God that was given to the whole world…is the Son of God…. The great and glorious Angel Michael is He Who has authority over this people and governs them [Daniel 10:21 & 12:1 cf. Revelation 12:7].   For this is He Who gave them the Law into the hearts of believers.   He accordingly superintends them to whom He gave it, to see if they have kept the same."