How to snap two obj objects together in unity so that they dont overlap but touch each other.

I want to align an object so it ouches another object.

Depending upon your situation, look at the instructions for either surface or vertex snapping in the Unity manual regarding manipulating game objects.

From the manual on vertex snapping:

Follow the steps below to use vertex snapping:

  1. Select the Mesh you want to manipulate and make sure the Move tool or the Transform tool is active.
  2. Press and hold the V key to activate the vertex snapping mode.
  3. Move your cursor over the vertex on your Mesh that you want to use as the pivot point.
  4. Hold down the left mouse button once your cursor is over the vertex you want and drag your Mesh next to any other vertex on another Mesh.
  5. Release the mouse button and the V key when you are happy with the results (Shift+V acts as a toggle of this functionality).

Unity doesn’t offer edge snapping by default

You might find this useful for edge snapping