Why and how do some metals oxidize and others become reduced?

Metal oxidize means lose of electron (Reducing agent) ==> Same time it reduces to other.

Metal reduce means gain of electron (Oxidizing agent) ==> Same time it oxidizes to other.

If metal has more negative potential ===> reduces to other metal

If metal has more positive potential ===> oxidizes to other metal

Li metal reduces to all other metal because it has highest negative potential.

Step-by-step explanation

2Li + Ba²⁺ ----> 2Li⁺ + Ba

Li oxidized and Ba²⁺ reduced.