Fire and air across the axis
Air supports fire, and across an opposition the support is unusually visible. Libra can articulate what Aries is doing, which Aries cannot always do for itself, and Aries can act on a conclusion Libra reached weeks earlier and has been weighing ever since.
The elements do not fight. What fights is method. Libra keeps a decision open in order to keep it fair, and Aries closes it in order to get on. Each considers the other's approach a defect of character rather than a difference of style.
Both cardinal, both initiating
Modality is more decisive than element here, because these are two cardinal signs and both start things. Neither drifts and neither waits. That gives the pairing genuine drive.
It also means neither defers. Aries initiates by announcing; Libra initiates by proposing and then requiring agreement. The friction is not that one leads and one follows. It is that both are leading, and one of them has made the process consultative in a way the other reads as delay.
Mars facing Venus
Aries is ruled by Mars and Libra by Venus, and the traditional literature treats them as a pair for a reason. Mars pursues, Venus attracts, and having them on either side of a relationship accounts for most of the pairing's reputation.
It is also why the pairing goes wrong in a predictable way. Mars pushes and Venus accommodates, and accommodation offered repeatedly stops being noticed. Libra keeps conceding and later presents a bill Aries did not know it was running up. The condition of Mars and Venus in the two charts decides whether that happens at all.
Where it grinds
Conflict itself. Aries argues immediately and cleanly and considers it healthy. Libra avoids the argument, agrees in the moment, and carries the objection privately. The result is that Aries thinks matters are settled when they are not.
The second point is other people. Libra maintains a wide set of obligations and cannot easily disappoint any of them. Aries regards most of those obligations as optional and says so, which Libra finds crude and does not forget.
Why the Suns are only a sketch
Sun-sign pairings describe averages across a very large group of people. Individuals differ from averages routinely, and this pairing in particular has a wide spread of outcomes.
Mars and Venus are the placements to compare, since they are the two rulers and they govern pursuit and affection directly. The Moons then show whether the two can be in a bad mood in the same room. That combination tells you far more than the Suns.
Questions people ask about this
Why are Aries and Libra considered a classic pairing?
They sit opposite each other and are ruled by Mars and Venus, the two bodies traditionally linked with pursuit and attraction.
What is the recurring argument?
How decisions get made. One closes them quickly and alone, the other keeps them open until everyone affected has been considered.
Does Libra really avoid conflict?
It tends to defer conflict rather than avoid it. The objection is held privately and surfaces later, often long after the other side thought the matter closed.
Which placements should I check?
Mars and Venus in both charts, because they rule the two signs, then the Moons. Those describe the pairing far better than the Suns.