What are some applications of model theory? In an attempt to "broaden my horizons", I am taking a class on model theory, which follows this book:
(Dead link)
Skimming through the chapters and reading wikipedia, I now have some slight idea of what it is about. However, I am still not clear on its applications (though application is not the primary reason I am taking this class).
Could someone enlighten me on why this field is needed, and as a matter of opinion, what are some of its potential application going forward?

If by applications you allow applications to other mathematical field, then here two examples.
The first one is Ax's theorem. It states that a polynomial function $\mathbb C^n \to \mathbb C^n$ is injective if and only if it is bijective. Basically, the proof is as follow : it is clearly true for (polynomial) functions $\mathbb F^n \to \mathbb F^n$ for any finite field $\mathbb F$ ; the Nullstellenstatz then implies that is also true for polynomial functions $\overline{\mathbb F}^n \to \overline{\mathbb F}^n$ with $\overline{\mathbb F}$ the algebraic closure of a finite field ; then comes the model-theoretic argument with Los's theorem which shows that it is again true in the ultraproduct of all algebraic closure of finite field. Then it can be seen that this ultraproduct is an algebraically closed field with characteristic $0$ and infinite transcendence degree over $\mathbb Q$, that is $\mathbb C$.
The second example is the Nullstellensatz itself. It is an immediat corollary of the model-completeness of the theory of algebraically closed fields.
