We can pass array of documents to the db.collection.insert () method to insert the multiple documents into the collection.
To create an array of documents, need to define the variable with some name and assign the array of documents to the created variable and then insert into Mongodb.

Syntax:                 var somename = [ array of documents ];
                           db.collection.insert(somename);

Example:               var Student_data =
                        [
                                    {
                                     Student_name : "Raghav",
                                     Department   : "Computer Science and Engg",
                                     Percentage   : "76%",
                                     Address         : { Street:"Burkit Road", City : "chennai",State:"Tamil Nadu" },
                                     Gender                       : "Male"
                                    },
                                    {
                                     Student_name : "Asthosh",
                                     Department   : "Computer Science and Engg",
                                     Percentage   : "72%",
                                     Address         : { Street:"Gandhi Road",City : "Hyderbad",State:"Telangana" },
                                     Gender                       : "Male"
                                    },
                                    {
                                     Student_name : "john",
                                     Department   : "Computer Science and Engg",
                                     Percentage   : "65%",
                                     Address         : { Street:"nicholus Road",City : "Chennai",State:"Tamil Nadu" },
                                     Gender                       : "Male"
                                    },                     
                        ];

   db.studentDetails.insert(Student_data)

After the successful insertion of data the resultant shows as below
BulkWriteResult
( {
"writeErrors" : [ ],
"writeConcernErrors" : [ ],
"nInserted" : 3,
"nUpserted" : 0,
"nMatched" : 0,
"nModified" : 0,
"nRemoved" : 0,
"upserted" : [ ]
})