Wikipedia's The nature of metallic bonding; In 2D says:
Graphene is an example of two-dimensional metallic bonding. Its metallic bonds are similar to aromatic bonding in benzene, naphthalene, anthracene, ovalene, etc.
Note: I've left the block quote here for continuity, but it's convincingly argued in comments and answer(s) that "metallic" is not the best way to describe bonding in graphene.
Most 2D materials currently studied tend to fall into two categories;
- 2D Xenes: flat or buckled honeycomb-like 2D structures like graphene, made from a single or alternating pair of elements. Examples include silicene, hexagonal boron nitride (h-BN), single layer black phosphorus (phosphorene) and both the hexagonal and asymmetric washboard forms of bismuthene are also examples (cf. Structure dependent optoelectronic properties of monolayer antimonene, bismuthene and their binary compound) For even more, see also The Rise of the Xenes: From the Synthesis to the Integration Processes for Electronics and Photonics
- TMDs:Transition metal dichalcogenide monolayers
(as an aside, these 2D materials usually also form van der Walls stacks analogous to graphite)
Question: Of these or others, are there any 2D materials whose bonding can be best described as metallic rather than covalent?