The Galaxy S6 has wireless charging. The HTC One M9 does not. There's a pretty good reason for this: metal interferes with the current methods for wireless charging, so you can't have your fancy metal phone and charge it (wirelessly) too. Engineers at Qualcomm have a solution to that, at least according to the company's latest press release. It's a newly-announced functionality of the existing Rezence wireless power standard, which is different from Qi and PMA.

According to Qualcomm, the Rezence/WiPower standard operates at a frequency that's more forgiving of extra material in between the contact and the receiver, including everything from metal to empty space.