Moving electrons accompanied by Jahn - Teller phonon and spin-wave clouds may form composite polarons in ferromagnetic narrow-band manganites. The ground-state and finite-temperature properties of such composite polarons are studied in the present paper. By using a variational method, it is shown that the energy of the system at zero temperature decreases with the formation of the composite polaron and the composite polaron behaves as a Jahn - Teller phononic polaron; the energy spectrum of the composite polaron at finite temperatures is found to be strongly renormalized by the temperature and the magnetic field. It is suggested that the composite polaron contributes significantly to the transport and the thermodynamic properties in ferromagnetic narrow-band metallic manganese oxides.