Can mixing colors cause a reaction like bubbles or cause it to look more mettalic, simply because of that or does it depend on the paint chemicals in the product

It depends on the paint chemicals. You mentioned bubbles, which refers to production of gas. This would be a chemical change. And although you can mix a metallic pigment to create a hybrid of color and metallic pigment, the chemicals within the metallic pigment would definitely differ atomically structured. After all, the metal particles within the paint picks up and reflect light, hence the shine. (Depends on what type of metallic paint however).