Did you know, according to the Bible, God rarely appears in human form? It isn't God but Yahweh (the Lord) who mainly appears to patriarchs and prophets:
“When a prophet of the Lord is among you,
I reveal myself to him in visions,
I speak to him in dreams.
But this is not true of my servant Moses;
he is faithful in all my house.
With him I speak face to face,
clearly and not in riddles;
he sees the form of the Lord.
Why then were you not afraid
to speak against my servant Moses?” Num 12:6b-8
He sees the form of the Lord, not the form of God. There is a subtle difference. The Hebrew word for Lord (NIV), or LORD (ESV), is YHWH (probably pronounced 'Yahweh'). The Hebrew word for God is Elohim. If you search on Elohim and vision you only find a few references, all but one in Ezekiel, and none of them talk about God's form appearing.
The Lord, however, frequently appears to prophets:
Now Samuel did not yet know the Lord: The word of the Lord had not yet been revealed to him. 1Sa 3:7
The vision of Obadiah.
This is what the Sovereign Lord (Adonai Yahweh) says about Edom–
We have heard a message from the Lord:
An envoy was sent to the nations to say,
“Rise, and let us go against her for battle” Oba 1:1
(Adonai means 'lord' and is sometimes used in place of the divine name, Yahweh. In this case both are used.)
Often it is the angel of the Lord that appears, or a mysterious 'man' as in Gen 32 when Jacob wrestles with a 'man' who turns out to be God (Elohim), in a rare case of God appearing in human form. Sometimes men turn out to be angels and one of the angels turns out to be the Lord, as in Genesis 18. There the readers already know, right at the beginning of the story (v1), that it is the Lord, but Abraham only sees three men (v2).
So, what can we learn from this? That when Christians say 'Jesus is Lord' we are identifying Jesus with the Yahweh of the Old Testament, the God who reveals himself and makes covenants with Abraham, Isaac and Jacob and eventually with the Israelite people, the descendants of Jacob. In a sense little has changed. We move from Old to New Testaments and find that God is still God, and He is revealing himself to us, and coming down in human form, and identifying with us. Amazing!