Interfacing SD card (SDSC) with Arduino Mega 2560 without SD module
The typical SD card modules people sell for use them with Arduino and similar boards are simply intended for use with the legacy SPI mode supported by many SD cards. All they do is break out a SD card socket to pin headers for connecting to your microcontroller - they don't include a dedicated SD card controller.
However, SD cards are not 5V tolerant, so if you are using a 5V Arduino Mega, then you will need to level shift the signals, either using resistive dividers (low speed, flakey) or a dedicated level shifting IC (practically any will do). Many of these breakout boards will provide the level shifting.