Yes, there is a capital letter after an exclamation mark, but it depends on the context of the sentence.
In standard English grammar, if the exclamation mark ends a complete sentence, the next word should begin with a capital letter. For example:
“Wow! That was amazing!”
However, if the exclamation mark is used in the middle of a sentence, the following word does not need to be capitalized:
“I can’t believe it’s true! what a surprise.”
So, it’s important to consider whether the exclamation mark is concluding a sentence or interrupting one to determine if you should capitalize the next word.