Why are 80% of the elements metals in the periodic table??

It has to do with the electronic config, and the outermost electrons. Note the two groups on the left - alkali and alkaline earth from period 2 and down, they are metals. The groups in the middle 3- groups 3-12 (in periods 4-7) are the transition metals (they fill d-subshell). To the right is a region that has some metals, semi-metals, non-metals (in which the p-subshell progressively fills) and to the far right as the p-shell fills, they become gases, and farthest right column with full s²p⁶ configurations are the noble (monatomic) gases.