Can a metallic bond with a sea of electrons form inside the human body?
We may not produce nails from our bodies, but certain enzymes and proteins do involve metal clusters, especially clusters involving iron [1].  In the natural biomolecules iron-iron and iron-nickel compounds serve as functional groups for electron transfer.  Also discussed are iron-sulfur clusters, which have characteristics similar to all-metal clusters despite sulfur usually being considered a nonmetal.  Chemists have sought to mimic these natural cluster compounds with artificial molecules, not only using iron and nickel but also moving on to less common metals such as molybdenum and ruthenium.
Reference
1.
C. Fehl C and B.G. Davis, &quot;Proteins as templates for complex synthetic metalloclusters: towards biologically
programmed heterogeneous catalysis.&quot;, Proc. R.
Soc. A 472: 20160078. (2016)
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