How can I transform rows to columns?

Question

I have this table with data below and need help because I don't know which formula can I use to convert the table into the desired one.

I don't know if it's possible with ARRAYFORMULA, QUERY or TRANSPOSE

Current Data Set:

Date	E1	E2	E3
4/01/2021	4,17%	3,53%	3,16%
11/01/2021	4,40%	3,69%	3,58%
18/01/2021	4,93%	4,39%	4,10%

Expected Output:

Date	Type	Metric
4/01/2021	E1	4,17%
4/01/2021	E2	3,53%
4/01/2021	E3	3,16%
11/01/2021	E1	4,40%
11/01/2021	E2	3,69%
11/01/2021	E3	3,58%
18/01/2021	E1	4,93%
18/01/2021	E2	4,39%
18/01/2021	E3	4,10%

Data Set (Google Sheets)

Answer 1

use:

={"Date"\ "Type"\ "Metric"; INDEX(QUERY(SPLIT(
 FLATTEN(A2:A6&"×"&B1:L1&"×"&B2:L6); "×"); 
 "where Col3 is not null"; ))}