Yes, both twisted cords and coiled cords can be composed of several conductive materials such as copper, aluminium or fiber optics. The outer material used for the sheath might be PVC, silicone or TPE and others. Material selection is based on what the cable will be used for – flexibility; toughness; resistance to chemicals, temperatures and abrasion among other factors. Braided cables in particular may also feature an extra layer made from metal or cloth which acts as shielding against electromagnetic interference (EMI).