  The focus of the present thesis is on the analysis of gauge symmetry and its
various impacts on gauge theories. In the first part of this thesis, we have
studied different aspects of symmetries in connection with various field and
string theoretic models. The manifestations of gauge symmetries and their
interconnection with the diffeomorphism invariances have been discussed in the
context of different generally covariant models like string, membrane,
$p-$brane and metric gravity. Analysis of interacting string with proper
inclusion of the stringy boundary conditions led to the noncommutative nature
of the string coordinates. In the second part of the thesis the emphasis was
primarily on the impact of gauge symmetries on the field theories defined over
noncommutative space-time. The correspondence between the NC gauge symmetry and
ordinary gauge symmetry manifest by Seiberg--Witten maps between the NC gauge
fields and ordinary gauge fields have been used to construct equivalent
commutative theories describing the original NC gauge theories. Using this
commutative equivalent approach we have analysed several NC gauge field
theories of current interest. A upper-bound on the time-space noncommutative
parameter has also been worked out.
