Answer:
Atoms of metal.
Step-by-step explanation:
Metallic solids are a kind of solids which are held by metallic bond.
Metallic bond is formed between metal atoms. The metallic bond and metallic solids can be understand with the help of a virtual model known as "electron sea" model.
According to this, atoms are present in the sea of electrons (the valence electrons of metal atom). The electrons are free to move thus metals are conducting in nature. There is no specific bond between metal atoms so this gives more flexibility to metallic solids as compared to covalent and ionic solids.