通常有两种感叹句可供参考:
What + a (an) + 形容词 + 名词 + 感叹号!
What a beautiful butterfly!
(说明:what 是代词,代表后面的名词,侧重强调名词)
How + 形容词 + 名词 + be + 感叹号!
How beautiful the butterfly is!
(说明:how是副词,修饰形容词,侧重强调形容词)
顺便提一下,如果名词是复数,以上两句改为:
What beautiful butterflies!
How beautiful the butterflies are!