Love is a battlefield. - This is an example of -

Metaphor is an implicit comparison between two different things.
যখন কোনো বাক্যে দুটি ভিন্ন বা বিজাতীয় জিনিসের মাঝে পরোক্ষভাবে বা রূপকার্থে তুলনা করা হয় তাকে বলা হয় Metaphor।
যেমনঃ
- Time is money.
- Life is but a walking shadow.
- My life is local bus.
- Revenge is a wild justice.
- The world's is a stage.
- Love is a battlefield.


Simile:
A simile is an explicit comparison between two different things. Usually as and like are used in it. In simile the resemblance is explicitly indicated by the words. দুটি ভিন্নধর্মী জিনিসের মধ্যে As ও Like দ্বারা তুলনা বোঝালে তাকে Simile বলে। উপমেয়ের সাথে উপমানের সাদৃশ্য কল্পনা করা। যেমন: She is as innocent as a lamb.


Difference Between Metaphor and Simile
It can be difficult in some instances to distinguish between metaphor and simile as literary devices. Both are figures of speech designed to create comparisons. In fact, simile is a subset of metaphor. However, they are distinguished by the presence of one of two words: “like” and “as.” Metaphors create direct comparisons without using either of these words. Similes feature either like or as in making a comparison.


Source: An ABC of English Literature, Dr. M Mofizar Rahman.