  Since Facebook officially changed its name to Metaverse in Oct. 2021, the
metaverse has become a new norm of social networks and three-dimensional (3D)
virtual worlds. The metaverse aims to bring 3D immersive and personalized
experiences to users by leveraging many pertinent technologies. Despite great
attention and benefits, a natural question in the metaverse is how to secure
its users' digital content and data. In this regard, blockchain is a promising
solution owing to its distinct features of decentralization, immutability, and
transparency. To better understand the role of blockchain in the metaverse, we
aim to provide an extensive survey on the applications of blockchain for the
metaverse. We first present a preliminary to blockchain and the metaverse and
highlight the motivations behind the use of blockchain for the metaverse. Next,
we extensively discuss blockchain-based methods for the metaverse from
technical perspectives, such as data acquisition, data storage, data sharing,
data interoperability, and data privacy preservation. For each perspective, we
first discuss the technical challenges of the metaverse and then highlight how
blockchain can help. Moreover, we investigate the impact of blockchain on
key-enabling technologies in the metaverse, including Internet-of-Things,
digital twins, multi-sensory and immersive applications, artificial
intelligence, and big data. We also present some major projects to showcase the
role of blockchain in metaverse applications and services. Finally, we present
some promising directions to drive further research innovations and
developments towards the use of blockchain in the metaverse in the future.
