Novel layered metal iodides, with a van der Waals stacking structure and large average atomic numbers, suitable energy band-gap, strong magnetoelectric coupling effect, are regarded as a new type of photoelectric detection material, including high-energy ray detectors. Some magnetic 2D metal iodides can be used in magneto-electronic devices. Due to the strong potential for applications in opto-electro-magneto devices, they become a hot research topic in low-dimensional materials. Moreover, in terms of material preparation, the generally low melting points, mild and simple preparation conditions make layered metal iodides a good candidate to explore the growth mechanisms of two-dimensional layered materials. The structure and properties of 2D metal iodides are introduced in this paper, and then focus on the preparation of two-dimensional layered metal iodides. Finally, their applications in opto-electro-magneto devices are discussed. Hopefully, the readers will gain a better understanding of two-dimensional layered metal iodides and largely promote their future applications.