My Students often ask me "Should I practice with a metronome?" And my answer is usually always the same. Not until you know how to count your piece out loud and play it.
This is because a metronome helps you keep your counting even, and to maintain a certain speed. It won't tell you how long to hold a note. And it also won'tdifferentiate the fractionated time values within the measure. Your verbal counting does that.
"But I am counting in my head," my students say.
"Nope...you're not." I always respond.
That's because most of the time, they are not counting, at least not consistently. Everyone needs to count out loud at least a little while learning a piece as a beginner. The only exception to that is wind instrument players, since their mouth is kind of busy already playing their intsrument.
Lastly, before you can tolerate the non-stop ticking of the metronome, and actually follow very tightly to the set speed, you need to be able to play your piece. If you are struggling to find notes, or to acheive a difficult passage while the metronome is ticking away in the background, you will probably feel very annoyed by it, and want to throw it on the floor ...or possibly out of an open window.
So, do yourself a favour, count and learn your piece first, and the metronome is for the finishing touches for keeing an even tempo.