If models are not snapping together in Unity and appear to be transforming from the Center rather than the Pivot point...

then you need to go to the top left of your Unity window and where it says, "Center" click it and change to "Pivot". You may also need to delete a model you duplicated and re-transform it if you had already attempted moving it while it was incorrectly snapping. (Also, the global button switches between global and local transform space, just like Blender).