When two liquid droplets meet they coalesce to form a bigger droplet- this can happens partly because of the intermolecular force and partly because liquid has no definite geometric structure (so that they can flow and respond to the external disturbance). Now, when two solid material - say two iron rod come into contact they don't coalesce to form a single rod. Why? Is this because the iron rod has a definite structure and the intermolecular force is not large enough to break this structure and mould into a new one? When these two rods collide with sufficient kinetic energy, can't we expect them to weld together! Please explain in detail.