Abstract In this paper, we study a long existing open problem on Landsberg metrics in Finsler geometry. We consider Finsler metrics defined by a Riemannian metric and a 1-form on a manifold. We show that a regular Finsler metric in this form is Landsbergian if and only if it is Berwaldian. We further show that there is a two-parameter family of functions, ɸ = ɸ(s), for which there are a Riemannian metric 𝜶 and a 1-form ᵦ on a manifold M such that the scalar function F = 𝜶ɸ(ᵦ/𝜶) on TM is an almost regular Landsberg metric, but not a Berwald metric.
