Lance and Matt have little to interaction between the two. Their only canon exchange is during season four's "Black Site". After Pidge returns with her brother Matt, Matt and Lance meet for the first time. Once it's Lance's turn to meet him, Lance tells Matt, "Nice to meet you." Though moments later when Matt meets Allura, he is immediately infatuated with her and Lance quickly becomes jealous, making Matt back off. As soon as Pidge drags Matt to the Castle of Lions, Lance is seen behind them, groaning.
The pairing is more rare in the Voltron. It didn't have more vocal shippers till season 4. This is due to their limited screen time together. Matt shares most of his screen time with his sister, father and Shiro, while Lance spends most of his time with Hunk, Allura and the other paladins. They don't share any screen time together outside of their first meeting.
Since the two didn't have any interactions till season four, most fans already had preferred ships for the two. Both have very dominant fanon pairings, as well as semi-canon one's. Matt is mostly shipped with Shiro, and occasionally Allura. Lance is shipped more with Keith, Shiro, and Allura.
Those that do ship it, believe that the two would have some form of unresolved sexual tension. Specifically over a competition for Allura's affection. Other fans believe that there personalities are similar enough that they could bond over their more goofy traits.
On AO3, it is the third most written ship for Matt and the twelfth most written for Lance.
|SHIPS||het||Allurance • Allurivan • Hallura • Hidge • Hunay • Hunelle • Jamonica • Kacxa • Kallura • Kidge • Komelle • Krolidad • Krolivan • Leiffin • Lotacxa • Lotura • Mallura • Nymatt • Plance • Romatt • Romance • Shallura • Shidge • Zaggar|
|slash||Adashi • Corance • Hance • Heith • Jaith • Katt • Keitor • Klance • Koliveith • Lancelot • Latte • Shance • Sharkon • Shatt • Sheith • Shendak • Shlav • Shoran • Shotor • Shunk • Svance • Svav • Sveith • Uliro|
|femslash||Acxlura • Kromelle • Pallura • Romura • Shayllura • Veracxa • Zezor|
|poly||Jeiro • Klunk • Pallurance • Sheitor • Shkatt • Shklance|
|CHARACTERS||m/f||Allura • Hunk • Keith • Lance • Lotor • Matt • Pidge • Shiro|