It is of interests to ring theorists to study the properties of rings via properties of its modules. The book presents some consequences on a ring if some classes of modules over the ring are flat or generalized injective. The book has four chapters. The first chapter is a collection of preliminary definitions and results. Chapter two deals with some generalizations of ideals and duo rings. Chapter three studies some basic properties of von Neumann regular rings and the regularity of left SF-rings with some additional conditions. In Chapter four, rings are studied via generalized injectivity properties of modules over them.