The main purpose of this legislation, known as the Merchant Banking Modernization Act, is to update the rules governing merchant banking investments made by bank holding companies. Specifically, it aims to extend the time period that these companies can hold such investments from the current limit to a minimum of 15 years. The key provision of this act is the amendment to the Bank Holding Company Act of 1956. It allows bank holding companies to hold merchant banking investments for a period of at least 15 years.