Hvað hún syngur fallega!

No. Even though it starts with hvað, this sentence is an exclamation, not a real question.

Here hvað means something like how in English exclamations:

• Hvað hún syngur fallega! = How beautifully she sings!

A real question with hvað would usually mean what:

• Hvað syngur hún? = What is she singing?

The exclamation mark is an important clue here.

In Icelandic, hvað can be used in exclamatory sentences to intensify what follows. In that use, it is often best translated as how in English.

So:

• Hvað hún syngur fallega! = How beautifully she sings!

This is similar to English exclamations like:

• How nice!
• How fast he runs!

So although hvað often means what, in this structure it works more like an exclamatory how.

That is one of the most important things to notice in this sentence.

In normal Icelandic main clauses, the verb often comes early because of V2 word order. But in this kind of exclamative clause introduced by hvað, the word order is typically more like a subordinate clause:

• hún syngur
• subject + verb

So:

• Hvað hún syngur fallega!

not:

• Hvað syngur hún fallega! in this meaning

If you said Hvað syngur hún?, that would be a question meaning What is she singing?

So the lack of inversion helps show that this is an exclamation, not a question.

Syngur is the 3rd person singular present tense form of the verb syngja, meaning to sing.

So:

• ég syng = I sing
• þú syngur = you sing
• hún syngur = she sings

In this sentence, syngur means sings.

Fallega is an adverb. It means beautifully.

It comes from the adjective fallegur meaning beautiful. Icelandic often forms adverbs from adjectives with -lega.

So compare:

• fallegur = beautiful
• fallega = beautifully

In the sentence, fallega describes how she sings, so an adverb is needed.

Because the word is describing the verb syngur (sings), not the subject hún (she).

• If you describe she, you need an adjective.
• If you describe how she sings, you need an adverb.

So:

• Hún er falleg. = She is beautiful.
• Hún syngur fallega. = She sings beautifully.

That is why fallega is correct here.

The plain statement would be:

• Hún syngur fallega. = She sings beautifully.

The sentence in your example adds hvað to make it emotional or emphatic:

• Hvað hún syngur fallega! = How beautifully she sings!

So you can think of it as an exclamatory version of the basic statement.

Not very naturally.

A rough word-for-word breakdown is:

• Hvað = how/what
• hún = she
• syngur = sings
• fallega = beautifully

But natural English does not usually say What she sings beautifully! in this meaning. The natural translation is:

• How beautifully she sings!

So it is better to translate by structure and function, not just word by word.

A rough pronunciation guide for an English speaker is:

• Hvað ≈ kvath
• hún ≈ hoon
• syngur ≈ SIN-gur or SING-gur with Icelandic y
• fallega ≈ FAHT-lay-ga

A few useful notes:

• hv in modern Icelandic is usually pronounced like kv
• ð is a soft voiced sound, a bit like th in this
• ú is a long oo sound
• ll in Icelandic can have a special pronunciation depending on dialect and word; learners often need extra practice with it

A perfect accent takes time, so it is fine at first to aim for a careful approximate pronunciation.

Yes. This is a common exclamatory pattern in Icelandic.

For example:

• Hvað hún er falleg! = How beautiful she is!
• Hvað hann hleypur hratt! = How fast he runs!
• Hvað þetta er gott! = How good this is!

So the pattern is useful beyond this one sentence. It often expresses strong feeling, admiration, surprise, or emphasis.

Yes. A very common alternative is to use svo for emphasis:

• Hún syngur svo fallega! = She sings so beautifully!

This is slightly different in structure, but very natural. Compared with Hvað hún syngur fallega!, it may feel a bit more straightforward for learners at first.

Both are idiomatic, but the hvað version is especially good to learn as an exclamatory pattern.