Elastic search query in array of json object

According to your question, you have to return only the matching object from the array based on the query.

On the basis of Elasticsearch Array docs

Arrays of objects do not work as you would expect: you cannot query each object independently of the other objects in the array. If you need to be able to do this then you should use the nested datatype instead of the object datatype.

If you want to query on each object of the array and return only the specific object from the array, you need to use a nested query with inner_hits. But for using the nested query, you have to create a new index with nested mapping

Adding a working example with index mapping, index data, search query, and search result

Index Mapping:

PUT <index-name>
{
  "mappings": {
    "properties": {
      "metadata":{
        "type":"nested"
      }
    }
  }
}

Index Data:

POST <index-name>/_doc/1
{
  "metadata": [
    {
      "key": "type",
      "value": "animal"
    },
    {
      "key": "animal",
      "value": "cat"
    }
  ]
}

Search Query:

POST <index-name>/_search
{
  "query": {
    "nested": {
      "path": "metadata",
      "query": {
        "match": {
          "metadata.key": "animal"
        }
      },
      "inner_hits": {}
    }
  }
}

Search Result:

"inner_hits" : {
          "metadata" : {
            "hits" : {
              "total" : {
                "value" : 1,
                "relation" : "eq"
              },
              "max_score" : 0.6931471,
              "hits" : [
                {
                  "_index" : "70711376",
                  "_type" : "_doc",
                  "_id" : "1",
                  "_nested" : {
                    "field" : "metadata",
                    "offset" : 1
                  },
                  "_score" : 0.6931471,
                  "_source" : {
                    "value" : "cat",
                    "key" : "animal"
                  }
                }
              ]
            }
          }
        }