malach? Shadal notes a three-way dispute.
That is, we could say that it is an "angel," as malach often means, in which case the angel has Hashem's name in him, whatever this means. Rashi says this. He writes:
כ] הנה אנכי שולח מלאך לפניך : הקדמונים פירשו מלאך רוחני ואתרים פירשו עמוד האש והענן, ולא יובן לפי זה מאמר ושמע בקולו ; ונ"ל כדעת רלב"ג שהמלאך הוא נביא, והוא משה, ולפי שחטאו ונתעכבו במדבר, לא הביאם הוא אל הארץ ומילא יהושע את מקומו,
[כא] כי לא ישא לפשעכם : אעפ"י שהוא ענו וסבלן, אין הסליחה בידו, ואם תקניטוהו אני אענוש אתכם, כי חייבים אתם לשמוע בקולו מפני ששמי בקרבו וממני כל דבריו. שמי : אלהותי, ע"ד הנה שם ה' בא ממרחק ( ישעיה ל' כ"ז ). כי שמי בקרבו : מחובר לראש המקרא, השמר מפניו כי שמי בקרבו ( רש"י ), והוא נגד הטעמים, ולפי מה שפירשתי ייתכן גם לפי הטעמים.
[כב] אשר אדבר : כי כל דבריו דברי הם.
[כג] מלאכי : הנביא כמו למעלה, והנה לא אמר שהמלאך ישמיד האומות, אבל אמר והכחדתיו
Behold, I am sending an angel before you Here they were informed that they were destined to sin, and the Shechinah would say to them, “for I will not ascend in your midst” (Exod. 33: 3). -[From Exod. Rabbah 32:3]Rashi here refers to Shemot 33:3:
that I have prepared to give to you. This is its simple meaning. Its midrashic interpretation is:
that I have prepared My place is already recognizable opposite it. This is one of the verses that state that the heavenly Temple is directly opposite the earthly Temple. [From Midrash Tanchuma 18]
malach is instead of Hashem Himself. Furthermore, Rashi writes:
do not rebel against him Heb. ךְתַּמֵּר, an expression of rebellion הַמְרָאָה, like “Any man who rebels (יַמְרֶה) against your orders” (Josh. 1:18).It seems unlikely that Tikkunei Zohar is Rashi's source, since Tikkunei Zohar is early 14th century. Rather, the borrowing would seem to be in the opposite direction. At any rate, it is clear that he considers this malach to be an angel, and specifically a special angel, Metatron (rather than the Transformer, the Decepticon named Megatron.)
for he will not forgive your transgression He is not accustomed to that [i.e., forgiving], for he is of the group that do not sin. And moreover, he is a messenger, and he can do only his mission. -[From Midrash Tanchuma 18]
for My Name is within him [This clause] is connected to the beginning of the verse: Beware of him because My Name is associated with him. Our Sages, however, said: This is [the angel] Metatron, whose name is like the name of his Master (Sanh. 38b). The numerical value of מֵטַטְרוֹן  equals that of שַׁדַּי . -[From Tikunei Zohar 66b]
Saying that an angel has God's name in him, thus granting him certain God-like status, can be quite theologically precarious.
Indeed, Elisha ben Avuya, according to Chagiga 15a, ended up concluding that there were two powers in heaven. And other sources refer to Metatron as "the Little YKVK." One example I encountered was in Bereishis Rabbasi, from Rav Moshe haDarshan, where he put forth the following (which seems echoed in other texts):
We see in Bereshit 5:
apotheosis. Hashem took away Chanoch's body of flesh and blood and replaced it with a body of fire. Hashem granted him thousands of ministering angels, gave him his own Kisei haKavod, and designated him YKVK haKaton.
A Chassidic Rabbi I know told me that they do not refer to Metatron by his full name, but just call him "Metat," somewhat akin to how one does not say the Divine Name.
This all seems theologically dangerous, but others who believe in this would counter that it is true. But especially dangerous, since people addressed prayers to Metatron. For example, See here.
We could interpret it otherwise. As Shadal notes, others interpret it as not referring to an angel but rather to the pillar of fire and smoke which traveled before the Benei Yisrael in the midbar. Shadal rejects this, for it states in pasuk 21 הִשָּׁמֶר מִפָּנָיו וּשְׁמַע בְּקֹלוֹ, אַל-תַּמֵּר בּוֹ -- "Take heed of him, and hearken unto his voice" which has no meaning in the context of a pillar of fire.
Rather, Shadal favors Ralbag's explanation, that this "malach" means "messenger," as it does in several other contexts in Tanach. This is no angel, but rather is Moshe Rabbenu. The meaning is then:
|כ הִנֵּה אָנֹכִי שֹׁלֵחַ מַלְאָךְ, לְפָנֶיךָ, לִשְׁמָרְךָ, בַּדָּרֶךְ; וְלַהֲבִיאֲךָ, אֶל-הַמָּקוֹם אֲשֶׁר הֲכִנֹתִי.||20 Behold, I send a messenger before thee, to keep thee by the way, and to bring thee into the place which I have prepared.|
Even though Moshe is indeed quite humble, patient and forgiving, this forgiveness is not his to give -- כִּי לֹא יִשָּׂא לְפִשְׁעֲכֶם. Rather, Hashem will punish this. What about כִּי שְׁמִי בְּקִרְבּוֹ? This is the reason Moshe cannot forgive, because it is Hashem who is the source of all of his words. This works out with the trup. Meanwhile, according to Rashi, this is connected with the first part of the verse, and Shadal connects this to Yeshaya 30:27:
This is a nice interpretation, which avoids the theological difficulties and dangers which indeed crop up from this verse.