In the wild, dogs make their homes in dens, and those instincts carry over to your pets. Most dogs love their crates, as they are a safe and cozy space. Your dog won't, however, love a crate that's too small and cramped for his body. Conversely, if the crate is too big, it may encourage bad behavior while he's put away. You need to find a happy medium based on his adult size.
Size is Relative
No matter the material of your dog's cage or crate, its size should be based on your pet's size. Ideally, a cage should be big enough for him to comfortably stand up, stretch and turn around in, but no bigger. If the cage is larger than that, he may not enjoy the feeling of enclosure that he ordinarily would -- he may even start using one part of the cage for sleeping, and another part for relieving himself. If you have a dog who is still growing, either rent a cage so that you can continue providing him with the right size, or invest in a cage with an adjustable barrier, so that you can expand the inside size as he grows into it.