John's tongue is full of sweet talking and poison.

Is the above sentence correct?

Thank you
It's grammatically correct. However, I would write
John's mouth is full of sweet talk and poison.
or any of a number of different sentences with similar meaning.
John is all sweet talk and venom.
John is a venomous sweet talker.

sounded ok to me.
 CalifJim's reply was promoted to an answer.