Passive verbs are a bit of a tricky topic for Korean. This is because passive voice is not used in the same way as it is in English, and isn't nearly as common in the same ways.
However, the passive voice is commonly used, just in different ways than it is in English. One of the most common ways passive voice is used is for making adjectives (when used directly before a noun). And one more common way that passive voice is used is to express "can" or "can't" as well.