Python: Inserting a list of lists into another list of lists

I would like to take the following lists:

matrix1 = [
[1, 2, 3, 4],
[5, 6, 7, 8],
[9, 10, 11, 12]
]

matrix2 = [
[A, B, C, D],
[E, F, G, H]
]

and combine them into:

new_matrix = [
[A, B, C, D],
[E, F, G, H],
[1, 2, 3, 4],
[5, 6, 7, 8],
[9, 10, 11, 12]
]

And I can't seem to figure out a good method. Insert() puts the whole list in, resulting in a list of lists of lists. Any suggestions would be appreciated!