Exclamations are often constructed with how and what. Exclamations with so and such are also common.

Exclamations with how
Exclamations with how are now considered a little formal or old-fashioned. In this construction how is followed by an adjective.

Blueberries ! How nice!

The structure ‘how + adjective/adverb + subject + verb’ is also posiible.

How beautiful she is! (NOT How she is beautiful!)
How beautifully she sings! (NOT How she sings beautifully!)

The structure ‘how + subject + verb’ is also possible.

How you have changed!

Exclamations with what

Common structures are: ‘what a/an + adjective + singular countable noun’

What a kind man! (NOT What kind man!)
What a beautiful flower! (NOT What beautiful flower!)
What a pleasant surprise! (NOT What pleasant surprise!)

what + adjective + uncountable / plural noun

What pleasant weather! (NOT What a pleasant weather!)
What beautiful flowers! (NOT What a beautiful flowers!)

What + object + subject + verb

What a beautiful smile you have!

Exclamations with so and such

Common structures are given below:

So + adjective

You are so beautiful!
He is so kind!

Such a/an + adjective + singular countable noun

Such a great experience! (NOT Such great experience!)

Such + adjective + uncountable / plural noun

They are such kind people! (NOT They are so kind people!)