Market order

MetaTrader 5 says execution of a market order results in a deal, and that a security is generally bought at the Ask and sold at the Bid. The price still depends on the execution mode. In market execution the broker chooses the price and sending the order is consent to that price. In instant execution the order carries the displayed price, and the broker either accepts it or returns a requote. CME's markets use a protected market order, which can trade only inside a pre-set price range, because an unprotected market order could fill at an extreme price. A market order does not name a worst price unless the venue's order type adds one.