Hangul – ㅁ M
This letter ㅁ (miem) is pronounced like an M. It is related to the Chinese word for mouth 口. It is related traditionally to the next letter in the Korean alphabet, ㅂ (bieup). You can remember the sound that it makes by either remembering that it is derived from the Chinese symbol for mouth or that it’s the shape of a letter that you get in the mail.
Read through more Hangul Lessons. You can also look at resources to learn to read Hangul.