  We have explored the low-temperature linear and non-linear electrical
conductance $G$ of metallic carbon nanotubes (CNTs), which were grown by the
chemical-vapor deposition method. The high transparency of the contacts allows
to study these two-terminal devices in the high conductance regime. We observe
the expected four-fold shell pattern together with Kondo physics at
intermediate transparency {$G\alt 2e^2/h$} and a transition to the open regime
in which the maximum conductance is doubled and bound by $G_{max}=4e^2/h$. In
the high-$G$ regime, at the transition from a quantum dot to a weak link, the
CNT levels are strongly broadened. Nonetheless, sharp resonances appear
superimposed on the background which varies slowly with gate voltage. The
resonances are identified by their lineshape as Fano resonances. The origin of
Fano resonances is discussed along the modelling.
