Deck screws are specifically designed to hold down timber or composite deck boards to structural timber or steel beams (joists) and are easily identifiable from standard wood screws. Typically they will have a parallel rather than tapered shank and most likely will have a self drilling and countersink feature enabling the screw to be fastened in one operation without predrilling the deck boards. Other features include corrosion protection by either a coating or manufacture from stainless steel and usually a high torque drive fitting such as square, hexagon and torx drives.
It’s important to realise that the self sinking and drilling features of all decking screws are designed for use in softer timbers such as pine etc, if used in hardwood decking boards then the timber would still need to be predrilled and pre-countersunk, these hardwoods, by nature, are simply too tough for any fastener to drive straight in.
For fixing boards to steel a wing tip self drill screw with a countersunk head is the preferred choice, again, these screws are designed to drill and fix in one operation, the wings drill a clearance hole in the timber (to prevent the board jacking up) and then snap off to allow the drill point to drill a hole in the steel and then tap a thread as it is driven in, securing the board to the steel joist in one single operation.