  Recently, intensive studies have revealed fascinating physics, such as charge
density wave and superconducting states, in the newly synthesized
kagome-lattice materials $A$V$_3$Sb$_5$ ($A$=K, Rb, Cs). Despite the rapid
progress, fundamental aspects like the magnetic properties and electronic
correlations in these materials have not been clearly understood yet. Here,
based on the density functional theory plus the single-site dynamical
mean-field theory calculations, we investigate the correlated electronic
structure and the magnetic properties of the KV$_3$Sb$_5$ family materials in
the normal state. We show that these materials are good metals with weak local
correlations. The obtained Pauli-like paramagnetism and the absence of local
moments are consistent with recent experiment. We reveal that the band
crossings around the Fermi level form three groups of nodal lines protected by
the spacetime inversion symmetry, each carrying a quantized $\pi$ Berry phase.
Our result suggests that the local correlation strength in these materials
appears to be too weak to generate unconventional superconductivity, and
non-local electronic correlation might be crucial in this kagome system.
