The higher the oxidation state of a metal, the more covalent its compounds are.
E.g. CrO is purely saline/ionic, and it is purely basic.
Cr2O3 is not really covalent, but also not purely ionic. It is both. It also reacts amphoteric and can be basic, but also acidic.
CrO3 is purely covalent, it has a low melting point, and it is purely acidic.
This trend is true for any element. So, SnCl2 is mostly ionic, SnCl4 is covalent. The latter is not a salt.
Yet another example: VCl2 is a salt, VCl3 we also still consider a salt, but it is not purely ionic. VCl4 is not a salt anymore, it is a brown liquid.
Metal compounds do not need to be salts. I have made some CrO2Cl2, which is a purely covalent compound of chromium, and which has a nice red vapor at room temperature. So, we can even have gaseous metal compounds.