In this chapter, we present an overview of the so-called modal methods for reduced order modeling. The naming is loosely referring to techniques that aim at constructing the reduced order basis for reduction without resorting to data, typically obtained by full order simulations. We focus primarily on linear and nonlinear mechanical systems stemming from a finite element discretization of the underlying strong form equations. The nonlinearity is of a geometric nature, i. e. due to redirection of internal stresses due to large displacements. Intrusive vs non-intrusive techniques (i. e. requiring or not access to the finite element formulation to construct the reduced order model) are discussed, and an overview of the most popular methods is presented.