Is it possible to have a device with metal case and wireless charging?
Wireless charging is currently most often done using a magnetic field (aka "near field" or inductive power transfer) and I'll assume that is what you mean.

If you can provide a metal free window then you can charge via it. Metal which intersects the field will have flux induced in it and there will be eddy current losses. With a window and suitable care you could minimise the field strength at the metal edges and keep losses low.

You can transfer power inductively through metal - you will incur eddy current losses whose magnitude will relate to the resistivity of the metal and it's thickness. Very thin metals and those of lower conductivity / higher resistivity will incur lower losses.

The transmit and receive coils are almost invariably resonated and voltage levels are far higher in the intended circuits than in the spurious ones. 

Despite various claims and patents, this system is far from new. If we ignore Tesla and a century + of transformers - I saw IPT demonstrated at a power level of hundreds of Watts in 1972 or 1973 - just under 40 years ago. Professor Don Otto of auckland University had a number of related patents 'way back then' and many modern claims to originality seem to be hopeful of spurious.