Reconstructive surgeries frequently require multiple, often complex, procedures at high social and economic costs. A shape-morphing implant that can be implanted using less invasive procedures and that then undergoes predesigned shape changes, leading to tissue expansion and allowing for complete degradation coupled with tissue regeneration, is a radically new treatment concept. BIOMET4D aims to create a new generation of shape-shifting and load-bearing implants for dynamic tissue restoration and to introduce a revolutionary paradigm in how actuators can be implemented in biomedicine. Science-towards-technology breakthroughs will be demonstrated with new shape-morphing metamaterials, 4D smart metallic actuators, advanced multi-domain optimization tools, and finally proof-of-concept for two potential clinical applications. Technologically, this vision also goes beyond existing paradigms because of the step-by-step actuation mechanisms, enabled through the additive manufacturing of multi-material degradable metallic structures, that are targeted for an order of magnitude improvement compared to the state-of-the-art. A futuristic long-term vision of this breakthrough technology is to dynamically regenerate entire tissues, such as a nose or an ear, and proof-of-concept will be demonstrated for craniosynostosis treatment and skin expansion. This long-term vision can only be achieved through an interdisciplinary approach and will likely have high social and economic impact as well as provide a new line of research for applications of smart metamaterials in medicine and engineering.