Stephen said
I am just concerned with what is meant by the Son of Man coming on the clouds of heaven. I always thought it refers to a human-like figure physically coming in the sky, literally above those witnessing him, because the language says, in translation “You will see the Son of Man coming etc…”. A well-known passage from Thessalonians tends to support this understanding. 

I would just quibble about the use of the word “literally” since in the sense you mean it is a modern concept.  What I would say is their viewpoint was concrete rather than abstract.  Yes I think they thought this was a True Story.

I think the “you will see” statement is just parroting back a couple of OT verses: (1) Daniel 7:13 that uses the periphrastic verbal expression “I was seeing”¹ that “with clouds one like a son of man was coming”;² and (2) Zechariah 12:10 that says that the people “will look to me whom they pierced.”³ I don’t know if the “they will see” (ὄψονται) was intended literally or not, given that seeing ghosts and visions used the same word. I imagine that they thought they would literally see Jesus (or whoever the son of man was supposed to be) coming on/in clouds with angels to judge the world.

Notes

1. Aramaic, חָזֵה הֲוֵית ḥāzēh hăwêṯ.

2. Aramaic, עִם־עֲנָנֵי שְׁמַיָּא כְּבַר אֱנָשׁ אָתֵה הֲוָא ʿim-ʿănānê šəmayyāʾ kəḇar ʾĕnāš ʾāṯēh hăwāʾ.

3. The Hebrew here is uncertain in meaning. It literally reads, “and they will look to me, whom they pierced.” This is followed by “and will mourn for him.” The switch in pronouns reads strangely, and the Biblia Hebraeca Stuttgartensiai (BHS) suggests repointing אֵלַי (“to me”) as אֱלֵי (“to” without a pronoun) or emending it to אֶל־ (“to”). אֵת אֲשֶׁר has also been explained as some kind of particle of reference, perhaps translated as “with regard to” or “on account of.” “They will look to me [God] on account of the one whom they pierced [Messiah ben Joseph?], and they will mourn for him…”

Omar6741 said
That is what it seems like to me.

By the way, are there any conventional metaphorical readings of the word “clouds” in this context? By “conventional”, I just mean metaphors that have become well-known and widely used in this context.

I’ve heard some interpret it as clouds of angels or clouds of saints (cf. Hebrews 12:1 for νέφος μαρτύρων “a cloud of witnesses” in reference to those mentioned in chapter 11). I think it intends us to really think of the clouds, given that Paul specifically mentioned “into the air” (εἰς ἀέρα 1 Thess 4:17), also mentioning “clouds” and saying that the dead would be coming “from heaven” to this same meeting. The dead are pictured as coming with Jesus from heaven, and the living are raised into the clouds to meet them. Given what Paul teaches about the resurrection (cf. 1 Cor 15), I don’t think symbolic clouds are in mind.

Note that Jesus is also supposed to have mentioned clouds with regard to the gathering of the saints (e.g. Lk 21:27). I don’t think this could all be coincidence or figurative language.

Omar6741 said

Thanks, jaihare. Have you heard of an interpretation according to which “coming with the clouds” is a metaphorical reference to coming with armies?  

Not necessarily, but that seems to be the position of the author of the Revelation:

“And the armies of heaven, arrayed in fine linen, white and pure, were following him [Jesus out of heaven] on white horses.” (Rev 19:14, ESV)
καὶ τὰ στρατεύματα τὰ ἐν τῷ οὐρανῷ ἠκολούθει αὐτῷ ἐφ᾿ ἵπποις λευκοῖς, ἐνδεδυμένοι βύσσινον λευκὸν καθαρόν. (Rev 19:14, SBLGNT)