MetaChat Protocol revolutionizes social communication via MetaMessage and MetaNetwork. MetaMessage consists of two major parts, AI Message and Smart Message. AI Message is developed based on GPT-4 and Stable Diffusion, and is configured to enlarge the scope of future communication from human-human to human-machine. Smart Message releases individual social capital by capturing the value spawned in daily social activities through embedded smart contracts. MetaNetwork is a unified social network built on Matrix, a decentralized communication protocol. It bridges different social networks to set the fundamental framework for universal messaging.