<p>I have searched the internet and found various 3D printers with different advantages and materials which they can print - some even multi color.  </p>

<p>However, I cannot seem to find a printer that can print multiple material with different properties; for instance, simultaneously printing PLA and metal. Is there currently such a printer available or in development? </p>

Yes and no.
for instance simultanious printing of plas plastic and lets say metal. Is such a printer available or in development ?
Practically speaking, no.  Metal printing requires significantly higher temperatures than plastic, and the two processes are so incompatible that there is currently no good solutions that would allow one printer to print both in the same print. Whether extruding filament, laser sintering, or curing resins, the materials involved have to be fairly similar in processing environment to print adjacent to each other without issue.
There are many printers that are intended to print multiple materials by changing the print head.  You might, for instance, use a ceramic paste extruder, then change the head for the next print using plastic.
There have been efforts in the past, and some efforts are ongoing, to resolve this.  For instance wood's metal, a low temperature alloy, can be poured at temperatures compatible with plastics, so it's possible to create a printer that prints plastic, leaving troughs or voids in the plastic, then the same printer during this print would pour molten woods metal into these areas, which then solidifies into an internal metal structure.  These are intended for circuitry and electrical use, however significant problems still exist because the thermal expansion differences in these materials lead to stress and result in poor reliability.
So while some of these processes are being developed, this is still just in the experimental stage and there are significant problems to overcome before printers can print widely different materials in a single printing session.
Of course you can find plastics with such a wide range of characteristics that they can be seen as printing different materials.  Plastics imbued with wood fibers, printing next to conductive plastics with graphite, printing next to flexible plastics, etc, etc are now possible, and depending on your requirements they may meet your needs.