  U-duality symmetry of M-theory and S and T-duality of string theory can be
used to study various black branes solutions. We explore some aspect of this
idea here. This symmetry can be used to get relations among various components
of the metric of the black brane. These relations in turn give relations among
various components of the energy-momentum tensor. We show that, using these
relations, without knowing the explicit form of form fields, we can get the
black brane solutions. These features were studied previously in the context of
M-theory. Here we extensively studied them in string theory (type II
supergravity). We also show that this formulation works for exotic branes. We
give an example of a time-dependent system where this method is essential.
