The metaverse has gradually come into the public eye and has become a hotspot in cyberspace, but it still faces many technical difficulties to be solved. Blockchain is a key component of the metaverse, enhancing the development of the metaverse by connecting the real and virtual worlds seamlessly and solving some of the difficulties faced by the metaverse. Our paper comprehensively studies the development and application of blockchain technology in the metaverse. First, there is an introduction to blockchain and the metaverse, followed by a discussion of why blockchain should be integrated into the metaverse. Second, an overview of the main blockchain technologies is provided to evaluate blockchain's role in the metaverse and the value is summarized. Third, the development of future integration of blockchain and metaverse is presented from the perspective of social life and technology. For social life, how to use blockchain in the metaverse to enhance and improve social life is discussed. Then, from the technical perspective, it discusses how blockchain shapes the metaverse. Finally, challenges associated with the integration of blockchain into metaverses are analyzed and some promising research directions and solutions are proposed.