双金属片是利用金属体积冷缩热胀的原理，将两种不同膨胀系数的金属片接在一起，当温度变化时，两者之伸长长度不同以致于向一边弯曲，来带动接点，使其接通或开路。

时钟

机械时钟的机械设备对温度的变化敏感，可能会导致钟表不能运转，从而不能正确指示时间，有些部件就会用双金属片补偿这种改变。最常见的方式是将摆轮的轮辋用双金属制成。

温度计

直接显示的度盘式温度计（例如室外温度计或肉类温度计）核心构件即是卷成一盘的双金属片。

Bimetal refers to an object that is composed of two separate metals joined together. Instead of being a mixture of two or more metals, like alloys, bimetallic objects consist of layers of different metals. Trimetal and tetrametal refer to objects composed of three and four separate metals respectively. A bimetal bar is usually made of brass and iron.