A student analyzes the bonding character in four different solid binary substances, \(Q\), \(R\), \(S\), and \(T\). The constituent elements and their Pauling electronegativity values are shown in the table below.

Substance	Constituent elements	Electronegativity of element 1	Electronegativity of element 2
\(Q\)	\(\text{K}\) and \(\text{Br}\)	\(0.8\)	\(3.0\)
\(R\)	\(\text{Ti}\) and \(\text{Al}\)	\(1.5\)	\(1.6\)
\(S\)	\(\text{C}\) and \(\text{O}\)	\(2.5\)	\(3.5\)
\(T\)	\(\text{N}\) and \(\text{Cl}\)	\(3.0\)	\(3.2\)

Based on the data in the table, which substance is best classified as a metallic solid held together by delocalized valence electrons?