SqlException: invalid column name even though it’s not the column

I am trying to insert basic data into my MSSQL database but I keep receiving this error:

System.Data.SqlClient.SqlException: 'Invalid column name 'Common'.
Invalid column name 'Bug'.
Invalid column name 'sac'.
Invalid column name 'sacas'.'

My query string is:

string query = "INSERT INTO dbo.RNMCommits ([Function], Date, Severity, ChangedBy, Changes)";
query += string.Format(" VALUES ({0}, {1}, {2}, {3}, {4})", function, date, severity, changedBy, changes);

I do not understand the exception, it says that column names Common, Bug, sac, sacas are invalid, but I am not using these as column names. I am stating in the INSERT statement that it should use ([Function], Date, Severity, ChangedBy, Changes)"; and insert VALUES VALUES ({0}, {1}, {2}, {3}, {4})", function, date, severity, changedBy, changes) which is common, bug, sac and scas.

These values are strings:

string function = comboBoxEdit_Function.SelectedItem.ToString();
string severity = comboBoxEdit_Severity.SelectedItem.ToString();
string changedBy = textEdit_ChangedBy.Text;
string date = dateEdit_Date.Text;
string changes = memoEdit_Changes.Text;

The whole method that gets executed:

    private void simpleButton_OK_Click(object sender, EventArgs e)
{
    string function = comboBoxEdit_Function.SelectedItem.ToString();
    string severity = comboBoxEdit_Severity.SelectedItem.ToString();
    string changedBy = textEdit_ChangedBy.Text;
    string date = dateEdit_Date.Text;
    string changes = memoEdit_Changes.Text;

    SqlConnection cnn;
    string connectionString = "Data Source=localhost;Initial Catalog=L3T_Project_Assistent;User ID=xx;Password=xx";
    cnn = new SqlConnection(connectionString);
    cnn.Open();

    string query = "INSERT INTO dbo.RNMCommits ([Function], Date, Severity, ChangedBy, Changes)";
    query += string.Format(" VALUES ({0}, {1}, {2}, {3}, {4})", function, date, severity, changedBy, changes);

    SqlCommand myCommand = new SqlCommand(query, cnn);
    myCommand.ExecuteNonQuery();

    cnn.Close();
}

Answer

When passing varchar/nvarchar/text values you need to wrap them in single quotes:

string.Format(" VALUES ('{0}', '{1}', '{2}', '{3}', '{4}')"