This study explores the intersection of Blockchain and the Internet of Things (IoTs), focusing on security challenges and potential use cases. With the exponential growth of connected IoT devices, reaching 16.7 billion in 2023 and projected to rise to 29 billion by 2027, ensuring the security of these devices becomes paramount. This study discusses the real-world applications of IoT in industries such as health care, agriculture, smart homes, smart cities, and Industry 4.0 that highlights the critical role IoT plays in advancing automation and efficiency. Identifying security threats posed by the explosive growth of IoT, the paper proposes Blockchain as a solution to enhance the security of IoT devices. The integration of Blockchain with IoT is examined to address security concerns, such as data integrity, decentralization, identity management, and resource sharing. Despite the promises of Blockchain in enhancing IoT security, the paper discusses various challenges, including scalability, latency, energy consumption, and regulatory complexities.