Straight Cancel (Straight "Can")
This completely eliminates a previously placed order. Keep in mind, a futures “market” order cannot be canceled because it will be filled immediately.
Cancel/Replace (Modify)
This cancels and replaces a previous order by changing the price, type, or quantity, but you cannot replace the commodity or contract month. Depending on the futures trading platform being used, it might or might not be possible to modify a working order into a GTC (Good ‘Til Canceled) order designation.
In most commodity futures markets it is possible to cancel/replace a working stop loss or limit order into a market order, but futures contracts traded on the ICE exchange (Intercontinental Exchange), typically cannot be modified into a market order. In this instance, it is necessary to cancel the existing order outright, and enter a brand new futures order ticket to buy or sell the futures contract at the market price.