The suggestions above are fine. I usually encourage students to sell themselves a bit when making cold contact emails. Lead strong in the opening sentence, and make sure the resume you include focuses on strengths. You can sell one strength in the subject line, or you can request a meeting instead.
Make it clear that you are requesting the meeting to discuss working in their research group.
Subject: Meeting request to discuss research opportunities in your group
Good morning,
I am an undergraduate at (Big State U) majoring in Physics with a 4.0 GPA. My programming skills are strong, and I am looking for a research group where I can contribute. Reviewing your web page and recent papers suggests I may be a good fit in your group. My resume is attached. Is there a good time I can come by your office for 15 minutes this week to discuss it in person? Some times I am available during your posted office hours are ...
Best Regards,
Joe Physics Major
Don't be shy. Email them a couple times if needed, and then just show up. Have a paper copy of your resume in hand.