Not a lot of Apple iPhone case manufactures make metal cases that they usually interfere with the cellphone and GPS signals. Fortunately companies like Rokform are still churning out cases for the iPhone that are made of aluminum.
Priced at $89 the Rokform Fuzion+ has polyurethane inner layer and aluminum back plate. In the middle you will find a thin sheet of carbon fiber to increase its strength.
Rokform Fuzion+ for iPhone 5/5s features
CNC machined from aircraft grade aluminum
High-impact inner TPU shell
Ultra-light; weighs less than one ounce
Integrated magnet in the case
Removable carbon fiber back plate insert
Bonus adhesive polycarbonate/TPU iPhone car magnet mount
Compatible with all iPhone carriers
Rokform Fuzion+ Review
You will also find a magnet here that can be used with other accessories from Rokform.