Except monodentate ligand can all types ligand form ring ?

Yes, besides monodentate ligands, all other types of ligands such as bidentate, tridentate, etc., can form ring structures. This is because they have more than one donor atom that can bind to the central metal atom/ion, forming a ring-like structure. This is often seen in chelate complexes. However, it's important to note that the ability to form a ring also depends on the spatial arrangement and flexibility of the ligand, as well as the size and geometry of the metal center.