In recent years, there has been an explosion of exciting results involving charges in ultracold samples, both in hybrid atom-ion systems and in ultracold Rydberg gases. In atom-ion systems, the charge is located on a heavy center, while it is the light electron that is the main actor in ultracold Rydberg gases. In this presentation, we cover aspects of both types of charged systems. We first discuss charge exchange between atoms and ions, paying special attention to isotopic effects, and show that tunable resonances could be used to affect the process. We then explore scattering of Rydberg electrons in ultacold gases. Due to their exaggerated properties (long lifetimes, large size and polarizability, etc.), Rydberg atoms can shed new light onto few- and many-body physics, and open new research avenues. We will explore particular phenomena, notably exotic molecules and new binding mechanism, and the effect of strongly interacting atoms leading to the blockade mechanism and its application to quantum information. We will also explore the behavior of Rydberg atoms in an atomic Bose-Einstein condensate (BEC). Impurities in a BEC have attracted much attention and motivated investigations of a wide range of phenomena e.g., probing the superfluid dynamics or polaron physics. Here, we show that the interaction between the quasi-free Rydberg electrons and ground state atoms results in the exchange of collective excitations (phonons) leading to a Yukawa potential. We will discuss different regimes determined by the scattering length of BEC atoms.