救命呀!! metals and　plastic呀

Metals are very hard and often use as the part of desk and doors
Also use as mailbox.It was human most used material.
Plastic have two kind, both soft and hard, is can be said hard.
It more non-breakable than glass.But It will melt with heat.
These two material both had special properties that being
use by human.

plastic ........... less heat resistance囉~~ lighter, can be made into different things
metal 就more durable, 不過可能會氧化