What does "speak my mind" mean?

Hi to everybody!! Adrià here you have the chorus of Guilty (Blue) where I don't understand the expression "speak my mind":

CHORUS - (LEE)
If it´s wrong to tell the truth
Then what am I supposed to do
When all I want to do is speak my mind (speak my mind) - ALL
If it´s wrong to do what´s right
I´m prepared to testify
If loving you with all my hearts a crime - ALL
Then I´m guilty

(Ohh.. very beautiful! A great band! Je, je!)

Ah! Another thing! Now is my family who are ill, so I'll tell them your super-super sentence "don't worry, the summer is coming!" xD It's a great consolation xD

Thanks!!!!

Pili. -----> "What's up nennn!!" xDDDDDDDDD