Recent theoretical work on iron-containing systems relevant to biological processes is reviewed. Methods used for this include structural and energetic investigations at the ab intio electronic structure level and structural and dynamical work using molecular dynamics simulations, Results from  both approaches are discussed and their relevance to experimental work is assessed. It is concluded that understanding a biologically relevant process requires efforts from experimentalists, insight from electronic structure calculations and the assessment of dynamical effects through finite- temperature molecular dynamics simulations.