The two properties that applies to most elements that conducts heat is that they are malleable and they have free electrons.
Most substances that conducts heat readily are metals.
Metals are held together by metallic bonding.
For a metallic bonds to form, there must be attraction between the positive nuclei of all the closely packed atoms in the lattice and the electron cloud jointly formed by all the atoms by losing their outermost shell electrons.
The physical properties of metals such as malleability and conduction is due to this bond type.
