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Among the most puzzling features of high-temperature superconductors is the behavior of the resistive non-superconducting state, often called a strange metal phase. Recently, the magnetic field-dependence of the resistivity, the magnetoresistance, of these materials has become a topic of intense interest. In particular, a linear-in-field magnetoresistance, and an unusual scaling relation with temperature, have been observed as quite general and puzzling phenomena in strange metals. In this talk, I will discuss a magnetoresistance model based on orbital motion in the presence of the sharply anisotropic Fermi surface and scattering time induced by antiferromagnetic order and fluctuations. I will present new experimental data demonstrating the validity of this model both in the antiferromagnetically ordered and strange metal phases of P-substituted BaFe₂As₂. Finally, I will discuss the potential applicability of these models to a variety of high-temperature superconducting materials, and possible extensions to the off-diagonal component of the magnetoresistance tensor (the hall resistivity), which often exhibits anomalous behavior in these materials as well.