Even though animals can't technically "marry" (since that's something that only humans can do), there are some animal species who will mate and commit to each other for a long time. Over 90% of bird species are "socially monogamous" (meaning that the same two parents will help raise their babies); penguin dads will keep their eggs warm while mom goes off to look for food, while bald eagles will remain faithful to their mate until one of them dies! Other animals that mate for long periods of time include gorillas, dikdiks (a type of African antelope), and anglerfish.
A marriage itself is actually a legal contract! While a wedding ceremony can be a beautiful way for two people to show how much they love each other, married couples pay different taxes and have certain rights that other couples don’t. Since animals don’t need to worry about things like paying taxes or buying a house, a "marriage" isn't really necessary!