qué/cuánto/cómo

Spanish exclamatory sentences are a powerful way to express emotion. They often use the same words as interrogatives but with a different structure and tone, normally enclosed in paired exclamation marks (¡...!) when expressed as direct exclamations. Indirect exclamatives such as Es increíble cuánto sabe are embedded in a larger statement and do not require those marks.

1. Using ¡Qué...!
This is the most versatile exclamatory word. It can be followed by a noun, an adjective, or an adverb.

• ¡Qué + Adjective!: Emphasizes a quality. A clause may follow the adjective, or the verb may be omitted.
  ¡Qué inteligente es Ana! (How intelligent Ana is!)
  ¡Qué cansado estoy! (How tired I am!)
  
  
• ¡Qué + Noun!: Expresses surprise or admiration for a thing or concept.
  ¡Qué pena! (What a shame!)
  ¡Qué día! (What a day!)
  
  
• ¡Qué + Noun + más/tan + Adjective!: This structure is very common. You can also insert más or tan after the noun for extra emphasis, which is a very natural-sounding construction.
  ¡Qué casa más grande! (What a big house!)
  ¡Qué película tan aburrida! (What a boring movie!)
  
  
• ¡Qué + Adverb!: Emphasizes the manner of an action.
  ¡Qué bien cocinas! (How well you cook!)
  ¡Qué rápido pasa el tiempo! (How quickly time passes!)
  
  
• ¡Qué de + Noun!: An advanced structure used to express a large, surprising quantity. It's similar to cuánto.
  ¡Qué de gente hay en la plaza! (What a lot of people there are in the square!)

2. Using ¡Cuánto/a/os/as...!
This word expresses quantity or degree, including the intensity of a feeling.

• ¡Cuánto/a/os/as + Noun!: Cuánto acts as an adjective and must agree in gender and number with the noun it modifies.
  ¡Cuánta paciencia tienes! (How much patience you have!)
  ¡Cuántos amigos vinieron a la fiesta! (How many friends came to the party!)
  
  
• ¡Cuánto + Verb!: Here, cuánto acts as an adverb, modifying the verb. As an adverb, cuánto is invariable; it is not agreeing with a masculine noun.
  ¡Cuánto has crecido! (How much you've grown!)
  ¡Cuánto me alegro de verte! (How happy I am to see you!)

3. Using ¡Cómo...!
This word is used to express surprise at the manner or intensity of an action. It commonly quantifies a predicate. In both Spain and America, cómo also occurs with de + adjective later in the clause: ¡Cómo está de contenta! Some American varieties additionally allow cómo with ser and an adjective, as in ¡Cómo eres simpático! These have their own structures.

• ¡Cómo + Verb!: It emphasizes how an action is performed.
  ¡Cómo canta! (How she sings!)
  ¡Cómo se parece a su padre! (How much he resembles his father!)

Remember that these are different from interrogative sentences, which ask for information rather than expressing emotion. The context, intonation, and punctuation make the function clear.

Meaning And Accent
Qué, cuánto and cómo retain their written accents in both direct and indirect exclamatives. Qué + noun leaves the evaluated property to context: ¡Qué día! may express delight or frustration. Some quantity readings overlap, as in ¡Qué frío! and ¡Cuánto frío!; the contrast is not a universal quality-versus-quantity ban. Exclamatory más in ¡Qué casa más grande! does not by itself compare the house with every other house.