Metatarsal pads can be good way to treat callus under the ball of the foot (plantar callus). The most common reason for a callus under the ball of the foot is an overload on the metatarsal heads. The purpose of a metatarsal pad is to be placed just behind the metatarsal heads under the foot and that off loads some of the pressure on those metatarsal heads. The metatarsal pad can be stuck on the foot or stuck on an insole or placed in the shoe.
The other big advantage of a metatarsal pad is that it also forces the toes to take a greater share of the loads, further offloading the metatarsal area where the painful callus is.
Podiatrists often used metatarsal pads on foot orthotics for a number of forefoot problems such as metatarsalgia, Morton’s neuroma, plantar plate tears and plantar calluses. You can also find metatarsal pads online to do it yourself.