Metaphor has been used in this sentence because in an indirect way the lamp has been compared to experience of the speaker which helps and guides him during dark times.
Explanation:
Metaphor is one of the most commonly used devices in the literature by the writers or in the poems by the poets. It is one of the most interesting devices to be used which creates great impact on the reader of the story or the poem or where ever it is used.
Metaphor is basically used to make a direct comparison of one thing with the other which in general has no relation with each other. Making this comparison makes the text understandable and well read for the readers of the story or the poem. It has a great impact.
