To most people the word "lord" means "G-d." This was not the only meaning of the word in 17th century England when the King James translators chose this word for T'hillim / Psalm 110:1 where that translation has "The LORD said unto my Lord."
Notice that the King James translators chose to capitalize the first use of the word "LORD"?
In the original Hebrew psalm this is G-d's holiest name.
It is indeed speaking of G-d.
But did you notice that the second "Lord" in the King James translation is not presented in the same manner?
Only the first letter is capitalized. It is presented as "Lord" not "L-RD."
The translators made the two words appear different because even the King James translators knew that this was not the same word as the first -- it was not a name of G-d at all. In checking many Christian translations they all seem to mirror the King James -- they all use the word "lord" for the second party in this sentence.
Here is the Hebrew for T'hillim / Psalm 110:1:
לְדָוִד מִזְמוֹר נְאֻם יְהֹוָ-ה | לַאדֹנִי שֵׁב לִימִינִי עַד אָשִׁית אֹיְבֶיךָ הֲדֹם לְרַגְלֶיךָ
The first word translated as L-RD is G-d's holiest name in Hebrew (I added the hyphen as we are not to write out G-d's holiest name). The word is יְהֹוָ-ה.
The second word translated as "lord" is a totally different word. It is לַאדֹנִי.
Thus the list maker's contention that this psalm is saying that David's son is called G-d (L-rd) is untrue.
The first name is G-d's. The second one is a human master or "lord" -- not a god. The person G-d tells to "sit still until I defeat your enemies" is most likely King David himself, although some say the psalm is about Abraham and G-d defeating Abraham's enemies. Rashi (רבי שלמה יצחקי / R' Shlomo Itzachi, the great Jewish commentator 1040 – 1105) wrote: "Our Rabbis interpreted it as referring to Abraham our father, and I shall explain it according to their words (Mid. Ps. 110:1): The word of the Lord to Abraham, whom the world called “my master,” as it is written (Gen. 23: 6): “Hearken to us, my master.”"
Whoever is the subject of this psalm (Abraham or David) is not Jesus. Read the first line again: "Of David a psalm. The word of the L-rd to my master; "Wait for My right hand, until I make your enemies a footstool at your feet."
Did G-d defeat Jesus' enemies?
Were Jesus' enemies flung at his feat, defeated?
Of course not, Jesus' enemies killed him.
How then can a missionary claim this verse is about Jesus?
Only through mistranslation "Lord" as if it were a god instead of a human master, and through taking that word out of context (Jesus' enemies were not defeated).
The error by Christian missionaries to think that it is G-d being spoken of in both the L-rd and the master may come from a mistranslation into the Greek in the Christian bible. In Psalms there are two words: G-d's holiest name is the first and a word meaning a human master is the second.
However, in Matthew 22:44-45 the same Greek word is used -- the word kyrois. "The L-rd / Κύριος / Kyrios said to my Lord / Κυρίῳ / Kyrio: "Sit at my right hand until I put your enemies under your feet."' If then David calls him 'Lord,' / Κύριον, / Kyrion, how can he be his son?"' Matthew 22:44-45.
Later English translators compounded this mistake by using the word "lord" for both G-d and the human master even though they are different words in the Hebrew. On top of that they capitalize the initial letter of the word to read (Lord instead of lord) -- making it appear more divine / important than is found in the actual psalm.
Matthew 22:43-44 misuses this psalm -- ignoring the context of the psalm, but even so Matthew seems to use this not as a clear statement of anything but rather to ask the question of how King David could call Jesus "lord" if Jesus was his "son" (descendant). Good question, and Matthew does not answer it.
This psalm (T'hillim / Psalm 110) is a missionary favorite -- primarily due to the claim presented by the list maker here. Yet again innocent Christians who know neither Hebrew or Greek have been lied to and deceived. This is not a messianic prophecy.
Finally, if Jesus were a virgin birth as most Christians believe, and not the biological son of Joseph, he was not a son of David either. For more information on that subject I refer you to Jesus had no birthright to be a messiah - start at the beginning.