When we say that someone is "like an animal", it's not meant as a compliment. It means that someone has lost control and is violent or desperate.
However, I was lying on my back in the pool tonight, watching the sky. The birds and the dragonflies were flying above and me and I couldn't help but want to be like an animal. Not in the way that the phrase is often used but like an animal in the way that they are in the moment, flying through the air without a care or worry, not thinking about the past or tomorrow.