Mars is the planet that rules our drives and desires, including intimacy. The way you express yourself physically will have a great deal to do with where this planet was when you were born. If your chart has Mars in Libra, this is the energy that will most influence this aspect of your life. Note this is not about love or the pure expression of it, which is actually ruled by Venus. To learn more about your Mars sign, please see below!
Slow Burning Fire
Mars in Libra does not make rash decisions and they will not choose to jump into any sort of intimate situation without having thought it through very well beforehand. Why? Because they need to be sure it's the right decision and that all pros and cons have been carefully considered. It's not that they aren't sure they want to be spend intimate moments with a particular person, but rather that they aren't sure what follows will be in the best interests of either person. They will want to be sure you're treated fairly, and that they are as well. As you can imagine, this could hamper spontaneity, which can be very frustrating to other signs of a "fast burning" nature. Therefore, these Librans may want to consider someone with Taurus energy, as they are also prone to taking a long time to weigh the pros and cons of such encounters.
Following vs Leading
Mars in Libra is not going to sweep you off your feet and carry you into the boudoir. The idea would probably never even pass through their minds. They are very caring and sweet, but they are not swashbucklers. Nor do they long to be. If you would like your Libra to sweep you off your feet, you're probably going to have to tell them so. And you should probably also tell them how, where, and what time they should be there. It's not that they don't want to make you happy, it's just that they aren't driven by a need for intimacy. But that doesn't mean they don't understand that you might be, and if you tell them what you need, they will absolutely accommodate you. That said, if you're a fiery, passionate person, it may feel like they are just walking through the motions for you -- so if passionate expression is very important to you, this is probably not the sign for you, unless they've already got a passionate sun or Venus sign.
That Cheating Heart
Mars in Libra needs to feel that the relationship is 100% balanced and equal, or they will begin to resent their partner. And once they start to feel that way, they will become highly susceptible to outside temptations. Remember, Libra is a very charming sign that automatically attracts flirtations. If they are not feeling balanced in their own relationship, someone else who seems to understand them better will have a good chance of stepping in. It's not that Libra wants to cheat on you, it's just that if things are not balanced, they will feel as though the relationship is over anyway, and therefore being with someone else is justified. It will start out with emotional cheating, and then if it's not nipped in the bud, could easily lead to the physical sort. So take care to make sure your Libra is feeling happy and equal, lest you risk some hussy stepping in and scooping him up!