An option which in practice is only declared on the expiration date because the underlying metal can only be acquired at that time. The LME option contract, which in theory can be declared at any time prior to expiration, is effectively a European option because there is no economic benefit to early declaration.
Option that can only be exercised on the date of expiry. These typically trade in the OTC markets. For metals, expiry is the third to last day of the month since settlement. In crude oil, options expire OTC six days prior to the 25th of the month or three days before the underlying future expires. options