Laser-ablated late lanthanide metal atoms were condensed with pure hydrogen at 4 K, and new infrared absorptions are assigned to binary metal hydrides on the basis of deuterium substitution and density functional theory frequency calculations. The dominant absorptions in the 1330-1400 cm-1 region are identified as LnH3 complexes with very weak ligand bands near 3900 cm-1. With ytterbium, YbH and YbH2 were the major initial products, but YbH3 increased at their expense upon sample irradiation. Evidence is also presented for the LuH and ErH molecules and the tetrahydride anions in solid hydrogen.