Source: Yugioh Wikia
Once a player enters the Battle Phase, an Attack may be Declared. To do so, the player must have at least one monster in Attack Position, with exceptions being "Total Defense Shogun" and "Elemental Hero Rampart Blaster", who may attack while in Defense Position.
Attacks have no Spell Speed and do not use a chain[1]. You cannot chain to an attack, but you can respond to it.