  We study a configuration of a parallel F- (fundamental) and D- string in IIB
string theory by considering its T-dual configuration in the matrix model
description of M-theory. We show that certain non-perturbative features of
string theory such as $O(e^{-\frac{1}{g_{s}}})$ effects due to soliton loops,
the existence of bound state (1,1) strings and manifest S-duality, can be seen
in matrix models. We discuss certain subtleties that arise in the large-N limit
when membranes are wrapped around compact dimensions.
