Yes, metal roofing may affect the antenna signal if it is too close to the metal roof outside. The reason is very plain and simple that metals do not allow the radio waves to pass through them that easily. Metals are known to be good electrical conductors.
Many people who did not have metal roofing earlier have had their antennas working in good condition. There had been no problem until they re-roof with metal. It disturbed the signals and they ultimately had to remove the antenna to another location from being too close to it. It saved them from lot of problems.
If you have recently did a makeover of the roofing of your house and installed metal planks then you probably need something or someplace high to fix the antenna for undisturbed flow of signals to your television system and radio. In case it is not possible then you would need to replace the antenna or take some other necessary steps to remove the obtrusive metallic objects from affecting the signals. Many people solve this issue by simply using a long pole and fix their antennas on it away from the metal. However, if you are one of those or your lovely spouse does not want to put in any antenna believing it would destroy the outlook and grace of the house then you probably should change to a eaves mount or tripod antenna.
Getting a pole to put the antenna on it at least 3 foot above the metal top roof would work great for a majority of people. Keep the golden rule in your mind that the higher the antenna is installed the better the reception is so you can solve signal problem this way. Another way to get good signals is to buy an amplifier but if you increase the height of the antenna for installation then it may work and catch good signal without needing any supportive device.
Many people plan to install and fix their antennas on the roof of attic or mobile house. The problem of receiving poor reception may continue and RF signal for the television set will be blocked due to the metal roofing. Another problem that the house owner may face is the reflected signals due to the metal on the roof, as it will inhibit the radio and television signal and result in reception.
Besides the metal roof, other areas around the house with metal such as walls, aluminum window frames and mirrors can also block and become a major cause of poor reception or signals. Therefore, you can use the siding of the house, chimneys and poles to clear away the blocking of signals. So, more height will clear the obtrusion in the way of smooth reception, radio waves and television signals.