Creation of lithium metallic particles in LiH and LiD crystals irradiated with 4.6 MeV He+ ions has been studied by techniques of optical absorption and Rutherford backscattering. The crystal structure, shape and size of small lithium metallic particles have been found in samples irradiated with ion fluences of 1013-1014 cm-2 by optical absorption spectra. The particles of metallic lithium have the body centered crystal structure of the parent metal. The metallic particles have a shape of prolate spheroids with the form factor a/b ≈ 1.1. Their average size is equal to 20 nm. The process of acquisition of the metallic lithium particles has a single-stage character in the range of ion fluences of 1013-1014 cm-2. The Rutherford backscattering technique was used to find a critical value of the ion fluence of 2 × 1016 cm-2 resulting in the surface metallization of the irradiated crystal. The depth distribution of lithium in the irradiated crystal revealed the lithium metallic particles to be created less easily in LiD crystals than in LiH ones.