Although some have claimed otherwise, there are thousands that wear underwire bras through airport security each day without setting off the alarm. If you really want to avoid setting off the metal detectors at all costs, consider wearing an underwire bra with plastic, a strapless bra or a sports bra.
Disposable and Zippo lighters without fuel are allowed in checked bags. Lighters with fuel are prohibited in checked bags, unless they adhere to the Department of Transportation exemption, which allows up to two fueled lighters if properly enclosed in a DOT approved case.