The options screen is simple what it's called. There is the option to press help, select a language, or to disable or enable sounds and music during the entire gameplay.
Pressing the help button opens up you internet browser and takes you to the Metal Slug Defense page. There you more options to find out any answers to your questions.
This helps determine the language that the player is accustomed to reading. The optional languages are listed as the following:
(There may be future updates to this game, enabling for more features and languages)
This option will enable you to wether or not be playing with sound and music or not during your entire gameplay.