Fusion peptides are hydrophobic and conserved sequences located within glycoprotein ectodomains that protrude from the virion surface. Direct participation of fusion peptides in the viral membrane fusion phenomenon has been inferred from genetic analyses showing that even a single residue substitution or a deletion within these sequences may completely block the process. However, the specific fusion peptide activities associated to the multi-step fusion mechanism are not well defined. Based on the assumption that fusion peptides are transferred into target membranes, biophysical methodologies have been applied to study integration into model membranes of synthetic fragments representing functional and non-functional sequences. From these studies, it is inferred that, following insertion, functional sequences generate target membrane perturbations and adopt specific structural arrangements within. Further characterization of these artificial systems may help in understanding the molecular processes that bring initial bilayer destabilizations to the eventual opening of a fusion pore.