plain metal的用法和样例：
例句
- She was holding a teaspoon in her two hands, pressing her thumbs against it as if measuring her strength against the base metal.
她双手拿着一个茶匙，用拇指使劲按着它，好象同这块普通金属较量力气似的。 - Compared to ordinary metal armor, scale armor makes it a lot easier for warriors to move, significantly enhancing the mobility of the entire army.
与普通金属铠甲相比，鱼鳞铠甲能使武士行动更加自如，进而极大地增加了整个军队的机动性。
