Not quite.
Normal guitar pickups are high impedance,
(hi-Z) they want to drive 500,000 ohms or so.
Line level will happily drive 10,000 ohms or less.
A guitar will not.
Cheap mics, and even the famous Shure Green Bullet,
are also high impedance. All decent mics are low
impedance.
So to feed a "line level" input, you need to
amplify the signal.
To convert a mic or guitar level signal
from high impedance to low, you can use a cheap
(or expensive if you are a gear slutz)
transformer.