How can I express my motivation to join a Masters program if I have no experience in the area? I am planning to apply to a specific master program in Finance. I do not have any experience in Finance and have never worked in any project related to Finance. But I am very interested to study it because I want to enlarge my research area (which is in signal processing) and have more job opportunities in the future. I really believe that I can excel in the program if I study it.

Can you please help me in writing two or three sentences that can motivate my interest to a program although that I have no work experience on it? I am trying to write a cover letter and I need your help.
I assume that the new area isn't just a random choice. Think about what it was about that area that drew you to it and say some things about that. It would also be good to work in a bit about how your background and training makes this a natural trajectory for you. If you have read papers in the new area and find them interesting and think you can contribute to the ideas there, say something about that. 

Even your statement here that you want to broaden your horizons is positive, but, alone, it is worth only a little.