Is there a way to open Metro And Desktop apps at the same time? ...

... without closing/minimize the metro app?
When I'm working with Photoshop I always have my email open because of the meeting notes.
The problem I'm having now is that everytime I focus back on Photoshop, the mail app closes/minimizes by itself. The same thing goes with Skype

I know that you can open that tiny multitasking window on the side, but it's just not efficient.
Is there a way to remedy this?

are you referring to snap ?

Well, If you have two monitors, you can work on one in photoshop, and leave metro open on the other.

If you only have one, then you can use the Metro Snap feature. Move the mouse to the top of the screen an "grab" and drag the window to the left or right side, then start photoshop. You can also use WindowsKey-period hotkey to cycle through the snap positions.