Collective excitations result from interactions between atoms or electrons and are typically born from an ordered or correlated state, such as superconductivity, density waves, and magnetism. Phonons are a typical example of a collective phenomenon of the lattice that can be directly measured with apparatuses such as infrared and Raman spectroscopy. Magnons are another type of collective phenomenon involving electronic spin degrees of freedom. These collective modes are usually rendered in single-particle spectroscopy methods, such as STM and ARPES, or are too complicated to disentangle from other effects in electronic transport measurements. On the other hand, electromagnetic radiation is intimately connected to these excitations, which can be detected by measuring the complex dielectric function of the dynamic conductivity. In this talk, I will present and discuss our recent results on the optical spectroscopy of 2D magnets, such as magnetic van der Waals materials. We observe strong magneto-elastic effects and hybrid collective modes in the optical spectra as a function of temperature and magnetic field due to the intertwining of lattice, spin, and charge degrees of freedom in these exciting materials.