The integration of phase change materials (PCMs) and metal foam has been widely concerned recently. To decrease non-uniformity of uniform metal foam-PCMs, adaptive metal foam arrangement strategy with increasing porosity from inside to outside has attracted widespread attention. This work conducted a symmetric simulation model of vertical thermal energy storage (TES) tube validated by experiments, for optimization of adaptive metal foam arrangement in basic design (0.94–0.94–0.94). It was followed by assessing the performance of gradient metal foam structures that included 27 cases with radial foam gradients of larger porosity on the outside and smaller porosity on the inside. Results demonstrated that a smaller difference between the inside and outside subregions resulted in better thermal performance when the same porosity of the intermediate subregion was used. More intense natural convection with stronger liquid paraffin vortex could be obtained by an adaptive arrangement. With the same average porosity, the faster phase change evolution, which was influenced by the maximum promotion of stronger natural convection, was achieved by using a larger intermediate porosity and a larger porosity difference between the inside and outside regions. The optimal strategy (0.87–0.94–0.97) could significantly shorten the melting duration as maximal as 17.15% compared with the original uniform (0.94–0.94–0.94), which contributed to efficient vertical metal foam TES systems, also as light and cost-effective as possible while also avoiding sacrificing thermal capacity.