Generally, metallic character increases on going down the group and decreases on moving left to right.
Here, carbon is a non-metal, tin and lead are metals whereas silicon and germanium are metalloids.
On going down the group, carbon has the lowest metallic character as it readily accepts the electrons to complete the octet (less atomic radius, difficult to loose electrons) whereas lead has the highest metallic character as it is easy to loose electrons with increase in atomic radius.
Thus, metallic character increases from carbon to lead.
