I was totally startled to reach Book V of The Faerie Queene and encounter Talus, a servant given by the goddess Astræa to the young knight Artegall:

His name was Talus, made of yron mould,
    Immoueable, resistlesse, without end.
    Who in his hand an yron flale did hould,
With which he thresht out falshood, and did truth vnfould.

Talus goes around following orders and smiting the unjust (ie non-Christians, Catholics, people who look at you funny) with great vigour, and then drops out of the narrative at the end of the book.

He’s not the only metal human I have encountered in pre-Čapek literature (cf Homer’s animated tripods and robot women) but they are rare enough to be worth noting.