* My new pants are so comfortable, I could live in them. (This uses "pants" as a noun, referring to the clothing item.)
* The comedian's pants fell down during his act, making the audience roar with laughter. (This uses "pants" as a noun, and describes an action.)
* He was so excited about the promotion, he practically jumped out of his pants. (This is an idiom, meaning he was very excited.)
Let me know if you'd like more examples, or if you have a specific type of sentence in mind!