Adam won the gold medal, the best swimmer on the team, at the state this year

I don't exactly know what the question is, but seeing that it's under the 'English' category, I'm going to assume you want someone to correct the sentence. "Adam, the best swimmer on the team, won the gold metal at state this year." would be a proper grammatical sentence.

Adam, the best swimmer on the team, won the gold medal at the state this year.

Explanation:

That is the best way to re-phrase a sentence into the correct way.