Moltres: The woman is his weakness, in more than one sense. Besides that she plays all the jokes she can on him (burning his clothes, making him feel umcomfortable with the temperature around him, etc), she's really important to him. He worries more than he should sometimes because he knows how prideful she can be. Secretly, he might have strong feelings for her, but refuses to tell it to anyone.
Zapdos: Zapdos is another close friend to Articuno, even if that bird is always on a crisis or just being really too hyperactive. Sometimes, even Articuno feels he's talking to a stubborn child and feels the connection between them is really soft. Even so, he worries for Zapdos as he worries for Moltres, at the point of entering in rage and freeze everything in order to save them.
Lugia: Lugia is like a mother to him, and the other birds also. Even if he's the one that speaks less, Articuno will always go and talk with her about everything. He really trusts her without doubting about it and keeps making her feel that she's just more than "Boss" and "Lugia". They are friends and family.
Mew: He considers her a the little sister of the Legendary Pokemons. Mostly because she's really playful and all innocent around them. He doesn't want her to be sad or have to fight, so he plans to take her battles too. Secretly, he plays with her with nobody is watching to make her feel happy.
Mewtwo: He hasn't talked with him a lot, but he respects him. He spent a lot of time before he could "trust" him again, but then again, Mew looked really proud that Mewtwo was acting nice once more that he respected that. When he needs a technical advice, he seeks for his help.
Ho-Oh: He doesn't understand how Ho-Oh's mind works and why is he bitter towards Lugia. He shows him the respect he deserves, but usually he is the first to go against something he says that, according to him, shouldn't be done or said.
Raikou: To him, the lost brother of Zapdos. Both of them seem to be really energetic and troublesome most of the time, but besides that, he doesn't talk with him too much. Mostly because he feels he's not in the same plane than he is sometimes.
Entei: The relationship with Entei is not really amazing. He just talk with him when it's necesary but most of the time Articuno avoids meeting him.
Suicune: The only one of the dogs he talks most of the time during the meetings. Maybe because the two of them share a lot of things in common and both of them think alike most of the time. Articuno wouldn't call him "a close friend" but yes a "good co-worker."