  We propose a possible scenario for the new metallic conductivity of
underdoped and optimally doped cuprates. Charge carriers are assumed to be
large polarons which form a Fermi-liquid and Cooper-like pairs below a
crossover tempurature $T^{\ast}$. We use the Boltzmann equation to calculate
the conductivity of self-trapped carriers and the resistivity $\rho$ as a
function of temperature and doping for different cuprates. We show that various
anomalies in $\rho(T)$ below $T^{\ast}$ are caused by the competing
Fermi-liquid and BCS-like precursor pairing effects. Our results for $\rho$ fit
well with existing experiments and characterize high-$T_c$ cuprates with an
intermediate-coupling.
