This study explores the theoretical foundations, market dynamics, and strategic implications of mergers and acquisitions (M&A) within the U.S. capital market, aiming to identify key theories, assess previous research, and provide insights into corporate consolidation trends. The objectives include examining fundamental M&A theories, analyzing financial and regulatory market dynamics, reviewing valuation methods and post-merger integration challenges, and understanding the strategic implications for corporate growth and shareholder value. Using a literature review methodology, the study synthesizes academic research, industry reports, and empirical studies to evaluate theories such as agency theory, synergy theory, and resource-based perspectives alongside empirical evidence on deal structures, financing mechanisms, and post-merger performance. The findings indicate that financial synergies, market expansion, regulatory influences, and competitive pressures drive M&A transactions. Moreover, the study posits that for a successful M&A deal, due diligence, valuation accuracy, and integration strategies are key. The study also highlights the impact of evolving market conditions, technological advancements, and policy changes on M&A trends. In conclusion, M&A remains a vital strategy for corporate growth and market positioning in the U.S. capital market, though no single theory fully explains all M&A activities.