Social media marketing has become one of the most influential tools for the expansion and sustainability of small businesses in the modern digital era. Unlike traditional marketing channels that demand heavy financial investment and provide limited audience interaction, social media platforms offer cost-effective, interactive, and measurable promotional opportunities. Small businesses increasingly rely on digital networks to build brand awareness, connect directly with customers, promote products and services, and compete with larger firms. This study investigates how successful small businesses use social media marketing to achieve growth in terms of visibility, customer engagement, sales performance, and brand loyalty. The study adopts a qualitative approach based on case analysis of thriving small enterprises that effectively implement social media strategies such as content marketing, video promotion, influencer collaboration, paid advertising, customer relationship management, and performance analytics. It further evaluates the factors that determine marketing success, including content quality, consistency, customer interaction, strategic planning, and data-driven decision-making. The study also explores key challenges faced by small businesses such as limited financial resources, lack of digital expertise, algorithm changes, content saturation, and rising online competition. Finally, the research provides practical recommendations and discusses emerging trends including artificial intelligence, short-form video dominance, social commerce integration, and personalized customer experiences. The findings confirm that social media marketing is a critical driver of small business development and a powerful tool for long-term sustainability in the competitive digital environment.