If you're not attuned to a magic item that requires attunement, you benefit from none of its properties. But it is still an object (a sword, a suit of armor, a book, etc.) and functions as such. And it is magical.
A weapon that possesses multiple properties, such as +1, or +2 as well as an elemental enchant may be taken on a case-by-case basis.
Q: I have a +1 Flametongue
A: You lose the elemental bonus, but the sword is still a +1 magical weapon.
Q: I have a hammer of thunderbolts, it has +1 and other properties
A: The +1 is inherent to the hammer of thunderbolts, when not attuned, it is a hammer with a +1 bonus.