This is where the bird will spend a great deal of it's time. A good rule of thumb is that the bird should be able to stretch out its wings fully in at least one direction. If it is too large, a smaller bird could hang itself. A. Horizontal bars are nice for the birds because they're easy to climb. Vertical bars make it hard to climb, but don't fray long tail feathers.
Cages are now available that have vertical front and back bars and horizontal side bars.
This should please everyone. A. Anodized aluminum, Brass, stainless steel, wrought iron. There are epoxy painted cages as well. Some cages come in wood cabinets, and you can order custom designs to match your decor. The fancy stuff can be hard to clean, and the bird can get caught in it.