As an undergraduate on physics seeking a solid education on mathematics, I have recently stumbled upon some theories that make use of the formalism of Lie groups and Lie algebras.
In light of this, I would like to ask where should I look for references in order to learn more about Lie theory and, of course, about its applications on physics, especially in Quantum Mechanics.
Well from a point of view of Lie groups theory to be applied to physics there is an elementary book called "Lie groups, physics and geometry" by Robert Gilmore which deals with matrix groups, Lie algebras, even some operator algebras and a small bits on structure of Lie groups. It also includes the standard applications (quantum mechanics, Maxwell eqn.s,..).
But for the more general study of Lie theory one needs quite a bit of topology,differential geometry and algebra (beyond linear algebra.. its good to know things from say commutative algebra,algebraic groups.., so one can study the representation theory of Lie groups..). In this case i would recommend the book by Chevally "Theory of Lie groups".