Water on a clean glass surface tends to spread out while mercury on the same surface tends to form drops . (Put differently, water wets glass while mercury does not .)

Explanation

Water on a clean glass surface tends to spread out . Water wets glass because force of cohesion of water is much less than the force of adhesion due to glass .Hence water spread out on glass or stick to surface of glass.
In case of mercury force of cohesion due to mercury molecules is quite strong as compared to adhesion force due to glass .
Consequently , mercury does not wet glass and tends to form drops.