You can travel with car from Athens to Metochi in approximately 3 hours and less, by following Attiki Road and then the national road Athens-Corinth.
After the Isthmus you turn left towards Epidavros (Corinth Exit 10 - Epidavros). Drive for 30 minutes and reach the intersection towards Epidavros. You will also see quide posts for Poros or Spetses. Turn right to the intersection and under the bridge.
You follow the newly constructed road watching out for the sign writing Poros. There, turn left to Poros and reach Galatas from the coastal road in 30 minutes. Then continue through Plaka-Lemon Forest-Aliki and after half an hour you are in Metochi, where there is a parking space. From Metochi you travel across to Hydra.
Metohi is an area opposite Hydra where there is space or if you want a guarded parking lot to leave your car.
From Costa, Porto Heli, Kranidi, Ermioni or other areas of the Peloponnese or even from Athens, following the other route through Kranidi, you can reach Metochi by following the coastal road from Thermisia.