def is_matched(expression):
    """
    Finds out how balanced an expression is.
    With a string containing only brackets.

    >>> is_matched('[]()()(((([])))')
    False
    >>> is_matched('[](){{{[]}}}')
    True
    """
    opening = tuple('({[')
    closing = tuple(')}]')
    mapping = dict(zip(opening, closing))
    queue = []

    for letter in expression:
        if letter in opening:
            queue.append(mapping[letter])
        elif letter in closing:
            if not queue or letter != queue.pop():
                return False
    return not queue
