Use the structure '' What + ( a/an) + noun!'' to make exclamative sentences.
1. The weather is very awful. -> What an awful weather !
2. The meal is very delicious. -> What a delicious meal!
3. The boy is very clever. ->What a clever boy!
4. The pictures are very expensive . -> What expensive pictures !
5. The dress is very expensive . -> What an expensive dress!
6. The milk is sour. -> What a sour milk!