Iron Golem

Vigilance
Iron Golem attacks or blocks each combat if able.

Alchemy Horizons: Baldur's Gate

Once an iron golem is set to a task, it won't turn aside until that task is complete or it has been destroyed.

Adventures in the Forgotten Realms

If the Iron Golem can't attack or block for any reason (such as being tapped), then it doesn't attack or block. If there's a cost associated with having it attack or block, its controller isn't forced to pay that cost, so it doesn't have to attack or block in that case either.