Question

mercury is the only metal found in liquid state. can we use it as a electrolyte

Answer 1

No, Mercury itself cannot be used as electrolyte as it will not decompose on passage of electric current. However, combining Mercury with any other compound such as Hydroxide(OH) then Mercury can be used as electrolyte as it will ionize to Hg $^{+}$ and OH $^{-}$ .

Answer 2

Metals in general are not electrolytes, and they all conduct electricity, in solid or liquid form. That is because their atomic structure has electrons that are not attached to the nucleus and are free to move around the material.