From metal might be the phone frame that supports all the component, just like Xperia Z1 and Z2 and not the whole body like HTC One. I bet the silver frame we can see in the pictures is the metal they are talking about.
HTC G1 Dream/Motorola Milestone/Samsung Galaxy S/LG Optimus 2x/Samsung Galaxy S II/Samsung Galaxy Nexus/HTC One X/Samsung Galaxy Note 2/Sony Xperia Z/HTC One/Samsung Galaxy S4/Samsung Galaxy Note 3/Motorola Moto G/LG G3
LG Optimus 7
iOS: iPhone 5
Be nimble as a greyhound, as tough as leather, as hard as Krupp steel and so you shall be the German warrior incarnate.