Sometimes, you may want to load 3D models into your Unity project during runtime. While Unity does not provide a built-in solution for this, there are third-party plugins and packages available that can help you achieve this functionality. This requires your model files to be converted/exported as either GLB or GLTF file formats.
The glTFast package is a popular solution for loading models at runtime in Unity. It leverages the standard glTF format, which is widely supported and optimized for real-time applications. As Pixyz Loader is becoming deprecated, glTFast is the recommended solution for loading models at runtime. You can find more information and download the glTFast package from its GitHub repository (link above).