Hello Habibur sikdar,

see, in solids the molecules are rigidly packed and there is no space between them, so no space, so molecules cannot move from one place to another and has strong intermolecular forces and hence rigid(strong)..as if consider your fist and each finger as molecule. if they are fingers are tightly closed with no space between them is stronger than the fingures seperated with space. it is how and why the solids are rigid.

Hope, the answer is helpful.

All the best.