Question: Is it possible to trigger the share action from within a metro style app without using the charm bar?

Answer: 
It's not really recommended, but there is an API available. 

```
// javascript
Windows.ApplicationModel.DataTransfer.DataTransferManager.showShareUI(); 

// or C#
Windows.ApplicationModel.DataTransfer.DataTransferManager.ShowShareUI();

```

More info located @ <http://msdn.microsoft.com/en-us/library/windows/apps/windows.applicationmodel.datatransfer.datatransfermanager.showshareui.aspx>
the recommended way is to open a share contract and do it via charm.

one reason to doing so is that if all developers do it via charm. user will know exactly where to find the share feature across all app and it helps to keep the whole windows 8 ecosystem clean