  The Mori's projection method, known as memory function method is an important
theoretical formalism to study various transport coefficients. In the present
work, we calculate the dynamical thermal conductivity in the case of metals
using the memory function formalism. We introduce thermal memory functions for
the first time and discuss the behavior of thermal conductivity in both zero
frequency limit and in the case of non-zero frequencies. We compare our results
for the zero frequency case with the results obtained by the Bloch-Boltzmann
kinetic approach and find that both approaches agree with each other. Motivated
by some recent experimental advancements, we obtain several new results for the
ac or the dynamical thermal conductivity.
