Recently, I came across a theory called “M&M Theory”.
The Modigliani–Miller theorem (of Franco Modigliani, Merton Miller) is an influential element of economic theory; it forms the basis for modern thinking on capital structure. The basic theorem states that in the absence of taxes, bankruptcy costs, agency costs, and asymmetric information, and in an efficient market, the value of a firm is unaffected by how that firm is financed. Since the value of the firm depends neither on its dividend policy nor its decision to raise capital by issuing stock or selling debt, the Modigliani–Miller theorem is often called the capital structure irrelevance principle.
The key Modigliani-Miller theorem was developed in a world without taxes. However, if we move to a world where there are taxes, when the interest on debt is tax deductible, and ignoring other frictions, the value of the company increases in proportion to the amount of debt used. And the source of additional value is due to the amount of taxes saved by issuing debt instead of equity.
Modigliani was awarded the 1985 Nobel Prize in Economics for this and other contributions.