If you’re looking for a minimalist metal wallet, Ekster provides a good option with their Aluminum Cardholder. Constructed from Space-grade 6061-T6 aluminum with an expandable aluminum backplate the wallet has slots for up to 15 cards + bills. It also has the added benefit of blocking RFID signals. It comes in five attractive colors that match up with the colorways that Apple offers for their iPhones.
Available at Ekster for $59.