Metallic usually refers to a finish (paint, trim), meaning it looks(shiny/ highly reflective)or contains metal (old metallic paint had metal flake in it to give a glitter effect.)

No, it won't stick unless you prime it first.

Well most of the time they are made of plastic but sometimes they can be plastic coated in metal or a metallic finish

Bronze sandals are open shoes that have a goldish metallic finish. They are rather sleek and sexy looking. They can be comfortable to wear and durable.