Can you provide more info on what exactly you want to do you in your metro application?
UPnP APIs are not available in WinRT. If your UPnP device supports PNP-X then you can discover and pair your device using metro device settings UI. Once the device is paired, you can enumerate your device using Windows.Devices.Enumeration and retrieve the device
properties such as ServiceControlUrl, ServiceDescriptionUrl, ServiceEventSubscriptionUrl and IP address. Check the code snippet posted at
http://social.msdn.microsoft.com/Forums/en-US/tailoringappsfordevices/thread/d40b02e1-27cd-4103-879f-913c7658edf1.