  In this dissertation we use the gauge/gravity duality approach to study the
dynamics of strongly coupled non-Abelian plasmas. Ultimately, we want to
understand the properties of the quark-gluon plasma (QGP), whose scientifc
interest by the scientific community escalated exponentially after its
discovery in the 2000's through the collision of ultrarelativistic heavy ions.
  One can enrich the dynamics of the QGP by adding an external field, such as
the baryon chemical potential (needed to study the QCD phase diagram), or a
magnetic field. In this dissertation, we choose to investigate the magnetic
effects. Indeed, there are compelling evidences that strong magnetic fields of
the order $eB\sim 10 m_\pi^2$ are created in the early stages of
ultrarelativistic heavy ion collisions.
  The chosen observable to scan possible effects of the magnetic field on the
QGP was the viscosity, due to the famous result $\eta/s=1/4\pi$ obtained via
holography. In a first approach we use a caricature of the QGP, the
$\mathcal{N}=4$ super Yang-Mills plasma to calculate the deviations of the
viscosity as we add a magnetic field. We must emphasize, though, that a
magnetized plasma has a priori seven viscosity coefficients (five shears and
two bulks). In addition, we also study in this same model the anisotropic heavy
quark-antiquark potential in the presence of a magnetic field.
  In the end, we propose a phenomenological holographic QCD-like model, which
is built upon the lattice QCD data, to study the thermodynamics and the
viscosity of the QGP with an external strong magnetic field.
