会 or 可以

Both words can translate English can, but they answer different questions.

• 会 (huì) says what will probably happen: 明天会下雨 (It will rain tomorrow). To reassure someone, add 的 at the end: 他不会生气的 (He won't be angry). 会 also means a learned skill: 我不会游泳 (I can't swim, I never learned).
• 可以 (kěyǐ) asks for or gives permission: 我可以进来吗？ (May I come in?) 这里不可以拍照 (No photos here).

Quick test: will, is likely to or knows how to means 会. May, is allowed to means 可以.
能 (néng) covers being able to in a situation (我今天不能来, I can't come today). It overlaps with 可以, so it is not practised here.