You have the option of selecting the fill method of a market order yourself in the MetaTrader order window. This is not possible for pending orders and is specified by the server.
The following filling methods are available:
Fill or Kill (FOK):
With the FOK fill method, your order will either be executed at the fully requested volume or not at all. If the required volume to execute the order is not currently available in the market, the order will not be executed. However, the required volume can be filled by several offers available on the market.
Immediate or Cancel (IOC):
With IOC, partial execution is possible. If only a partial volume of the requested volume is available in the market, this part will be also executed at the next available price. The rest of the requested volume of the position will be deleted.
This fill method is usually only used for limit and stop limit orders. If an order is partially executed, the remaining volume will not be cancelled, but re-entered into the market for execution. The execution of the order is thus guaranteed, but the price may differ for different parts of the order. The return fill method is only applied if this has been activated in the Volatility Protections Settings.