You can easily visit Metropol Istanbul from both the Anatolian and European sides by public transport. Buses passing by Ataşehir Plazalar IETT bus stop at a 140 meters distance to Metropol Istanbul;
Shared taxis and minibuses from Burak Bey stop which is 120 meters away:
If you want to visit by metro from the Anatolian side you can get off at the Yenisahra stop on the M4 line and come to Metropol Istanbul by transshipment.
If you want to visit by metro from the European side you can go to Ümraniye or Üsküdar and then transfer to the Metropol Istanbul