Is Mountains of Clouds a metaphor?

Yes. "A huge mountain of clouds" (Fuentes, "A Letter to God," 1940) is a metaphor, not a simile. The test is one word: a simile would say clouds like mountains, and the sentence has no like and no as. It just names the clouds as a mountain. What it actually is, under the hood, is an "of"-genitive metaphor, the N1-of-N2 shape that hides a metaphor inside what looks like an ordinary possessive.

How Do You Tell a Metaphor from a Simile Here?

A simile keeps the two things separate and announces the comparison: "clouds like mountains." A metaphor drops the comparison word and identifies one thing as the other: "mountains of clouds," or "the clouds were mountains." If the sentence makes you feel a comparison without ever using like or as, you are looking at a metaphor.

Lencho's sentence, "When he came out for his noon meal, towards the north-east a huge mountain of clouds could be seen approaching" (Fuentes, "A Letter to God," NCERT First Flight, Class 10), does the second thing. No like, no as, and the clouds are named as a mountain. That is the metaphor.

Phrasing	Figure	Why
huge mountain of clouds	Metaphor	No like or as; the clouds are identified as a mountain.
clouds like mountains	Simile	Uses like to keep the two things separate.
clouds as massive as mountains	Simile	Uses as ... as, the comparison frame.
the clouds, mountains in the sky	Metaphor	Identification, no comparison word.

The reason the phrase fools so many readers is that the comparison is buried inside a possessive shape ("X of Y"). Nothing in the sentence flags I am being figurative. The figure does its work without ever raising a flag.

What Kind of Metaphor Is It?

It is an "of"-genitive metaphor: the construction N1 of N2, where N1 names what the thing resembles and N2 names what it actually is. "Mountain of clouds" reads as clouds that are a mountain. The mountain is the figurative term; the clouds are the literal one.

This shape is one of the most productive metaphor constructions in English, and one of the easiest to walk past. Because the sentence frame is a possessive ("a something of something"), the reader's eye treats it like ordinary description. There is no verb of identification ("is," "becomes") to mark the figure. The metaphor lives entirely in the noun phrase.

Other figures in the same shape:

• "a sea of troubles" (Shakespeare, Hamlet, 1603): troubles identified as a sea.
• "a mountain of work": work identified as a mountain.
• "a forest of hands": hands identified as a forest.
• "a wall of sound" (Phil Spector, late-1950s production technique): sound identified as a wall.

In every case the figurative term comes first and the literal term comes after the of. Spot the shape and you can name what the metaphor is doing without having to argue about it.

What Is the Figure Doing in the Lencho Story?

It is doing two things at once.

It gives you the scale: clouds the size of mountains, piled on the horizon, big enough that a farmer who has been watching the sky all morning would stop and look up. The metaphor is doing the work an ordinary adjective ("huge," "enormous") cannot. The reader does not picture very large clouds; the reader pictures mountains.

It also carries weight beyond size. A mountain is not just big. It is immovable, hard, threatening if it falls. The metaphor leans the storm forward. By the time the rain turns to hail in the next paragraph and destroys Lencho's crop, the figure has already told you the storm is mountain-shaped: something that can crush a harvest, not something that will pass.

Could It Also Be Read as Hyperbole or Personification?

It can be read as hyperbole. The clouds are not literally mountain-sized, and naming them a mountain overstates the case for effect. The test for hyperbole: would the claim be false if taken literally? Yes. So the size-exaggeration reading is fair, and a teacher who tagged the phrase as both metaphor and hyperbole would not be wrong.

It is not personification. Personification gives a non-human thing human qualities (feelings, intentions, actions a person performs). The clouds in Lencho's sentence are not given a face, a will, or an action. They are identified with a different non-human thing. The test for personification: is the object doing something only a person can do? No.

When a phrase can wear two labels, the question is which move defines it. Here, the defining move is identification (clouds = mountain), which makes the primary label metaphor. Hyperbole is a secondary effect riding on the metaphor's choice of vehicle, not the figure that organizes the phrase. If you can name only one figure, name metaphor.

The cleanest line between a metaphor and a simile is whether the sentence uses like or as: with it, simile; without it, metaphor. Once you can see the "X of Y" construction working as a metaphor, you stop hunting for the like that was never going to be there. "A sea of troubles," "a mountain of work," "a wall of sound," "a huge mountain of clouds": same shape, same figure, same move. The of-genitive is the metaphor doing its quietest work, and once you spot it, you spot it everywhere.