Some allege Satan is never spoken of metaphorically.
At least no one in this thread is saying that.
That a text that doesn't explicitly name Satan, cannot be about him.
If Satan isn’t mentioned then we should be
very careful about claiming a verse or passage is about him. This is how false teachings come about.
However, scripture metaphorically calls Satan a number of things: In Revelation 12:9 he is called a "dragon, serpent."
Rev 12:9 And the great dragon was thrown down, that ancient serpent, who is called the devil and Satan, the deceiver of the whole world—he was thrown down to the earth, and his angels were thrown down with him. (ESV)
It also actually states that the dragon and serpent are “called the devil and Satan.”
In 1 Peter 5:8 he is "a roaring lion".
1Pe 5:8 Be sober-minded; be watchful. Your adversary the devil prowls around like a roaring lion, seeking someone to devour. (ESV)
Peter tells us the roaring lion is the devil.
Jesus calls him the "father of lies" in John 8:443.
Jhn 8:44 You are of your father the devil, and your will is to do your father's desires. He was a murderer from the beginning, and does not stand in the truth, because there is no truth in him. When he lies, he speaks out of his own character, for he is a liar and the father of lies. (ESV)
Jesus first says their father is the devil.
Paul "an angel of light" in 2 Corinthians 11:14.
2Co 11:14 And no wonder, for even Satan disguises himself as an angel of light. (ESV)
Paul also clearly tells us it’s Satan who is the angel of light.
Therefore, to allege Isaiah 14:12-15 cannot metaphorically be about Satan is without foundation.
Actually, you have helped prove my point. With each of the metaphors you listed, the context clearly tells us who the metaphor applies to—Satan, the devil.
To be consistent then, when we look at the context of Isa 14 and read that it is a “taunt against the king of Babylon” (v. 4), we should understand that all the metaphor of Isa 14 applies only to him.
12 How you have fallen from heaven, morning star, son of the dawn! You have been cast down to the earth, you who once laid low the nations!
13 You said in your heart, "I will ascend to the heavens; I will raise my throne above the stars of God; I will sit enthroned on the mount of assembly, on the utmost heights of Mount Zaphon.
14 I will ascend above the tops of the clouds; I will make myself like the Most High."
15 But you are brought down to the realm of the dead, to the depths of the pit. (Isa. 14:12-15 NIV)
Everything said suggests it is Satan who "fell from heaven" and has been "cast to the earth". That cannot be said about humans.
Except that there isn’t anything to suggest it is Satan. Everything else outside of those verses is clearly speaking about a man, the king of Babylon.
Do you think metaphor applies only to Satan and not humans? Why can’t this be metaphor (and sarcasm) about the incredible height of arrogance and pride of the king of Babylon, to the point of defying God and thinking he could be like Him?
Note also that chapter 13 is an “oracle concerning Babylon,” regarding its judgement, and that the rest of chapter 14 is the same but concerning Assyria and Philistia. Then there the many chapters after chapter 14 with oracles of judgement against many other nations, with the judgement of the whole earth in chapter 24.
Same in Ezekiel, Satan metaphorically is called the King of Tyre
12 "Son of man, take up a lament concerning the king of Tyre and say to him: 'This is what the Sovereign LORD says: "'You were the seal of perfection, full of wisdom and perfect in beauty.
13 You were in Eden, the garden of God; every precious stone adorned you: carnelian, chrysolite and emerald, topaz, onyx and jasper, lapis lazuli, turquoise and beryl. Your settings and mountings were made of gold; on the day you were created they were prepared.
14 You were anointed as a guardian cherub, for so I ordained you. You were on the holy mount of God; you walked among the fiery stones.
15 You were blameless in your ways from the day you were created till wickedness was found in you.
16 Through your widespread trade you were filled with violence, and you sinned. So I drove you in disgrace from the mount of God, and I expelled you, guardian cherub, from among the fiery stones.
(Ezek. 28:12-16 NIV)
Except for Adam and Eve, no human was in the garden of Eden. The text obviously is speaking about Satan.
Again, as with Isa 14, Satan is not only not mentioned, but it is clearly stated to be a prophecy against the prince of Tyre. Again, can metaphor only be about Satan or can it apply to humans as well, to describe the excesses and state of people in general or one person in particular?
On the one hand you claim it is metaphor, but in the other take certain details to be literal so that they can only apply to Satan. Imagery about Eden in no way means that either Tyre must have been in Eden or it must be speaking of someone or something else. The nature of metaphor and poetry is that nearly anything can be made to apply.
In this case, just as with the king of Babylon, extreme pride to the point of believing himself to be God or a god, will result in the prince of Tyre (perhaps also symbolic for Tyre itself) receiving God’s judgement.
Again note that chapter 25 contains prophecies against other nations, chapter 26 is a prophecy against Tyre, and chapter 27 is a “lamentation over Tyre.” Chapters 29-32 and similar but about Egypt.