Shear modulus as a funtion of temperature

[SidVicious]

Why does the shear modulus of a metal decrease with increasing temperature, on an atomic scale?
Is it something to do with electrons gaining more energy allowing "layers" to slide around more easily??

 

[alxm]

Well, more to do with the nuclei gaining more energy. That is to say, the atoms are moving around more.
To give a simple, very generalized answer, you could simply think of it this way:
Energetically, you have to overcome an energy barrier to get the planes to start gliding. If the thing is warmer, it has more energy, so it takes less energy to cross over the barrier.
In terms of the positions of the atoms, you have to move them from the equilibrium position to the (higher energy) position where the 'gliding' starts.If the thing is warmer, the atoms are moving more and so a lot of them are already closer to the point they need to be at for 'gliding' to begin.