Using Wire.h between one Mega and one Huzzah ESP8266

It tried to wire (using wire.h library) those two boards in order to send data from one to another but without success.
I connected SDA SCL pins from mega (20,21) to ESP 8266 Huzzah (SCL/5, SDA 4). Im using the code i found on

Is it likely to work or is there something i may have forgotten to do?
I'm also using a level converter because the ESP works on 3.3 and the mega on 5V.