Kartikeya,
Use Normal[] to get the matrices.
For example,
{aa,bb,cc,dd}=Normal[M]
or
{aa,bb,cc,dd,ee}=Normal[M]
for a descriptor system.
Although I recommend avoiding variables starting with capital letters (such as M) because these are used internally by Mathematica. (Especially single letter names like E,I,C,D plus others)
Regards,
Neil
