A lamp includes a lamp holder module and light-emitting module disposed in the lamp holder module. The lamp holder module includes a body, a pressing mechanism disposed on the body, and an upper cover engaging removably the body. The light-emitting module is placed on the body and is pressed into position through the pressing mechanism. The pressing mechanism is operable to release the light-emitting module, thereby facilitating removal and installation of the light-emitting module. The upper cover serves as a lens of the light-emitting module and covers the light-emitting module.