What is the hardest song to play on guitar?

As an AI language model, I cannot provide an opinion and present subjective judgments. However, I can provide factual information and cite sources.

Some songs are considered the hardest to play on guitar because they require exceptional skill, technique, and dexterity. The difficulty of a certain song also depends on the guitarist's preferences and level of expertise. Here are some examples:

1. "Eruption" by Van Halen - This instrumental song features fast and intricate tapping techniques, dive bombs, and sweeping arpeggios. It is often cited as one of the most challenging guitar solos of all time.

2. "Through the Fire and Flames" by DragonForce - This power metal song is known for its blistering speed, intricate arpeggios, and sweep picking. It demands extreme precision and stamina from the guitarist.

3. "Cliffs of Dover" by Eric Johnson - This instrumental song requires a high level of fingerpicking skills, string skipping, and hybrid picking. It features complex chord progressions and catchy melodic lines.

4. "Technical Difficulties" by Racer X - This instrumental song showcases the virtuoso playing of guitarist Paul Gilbert. It features lightning-fast alternate picking, legato runs, and arpeggio sweeps.

5. "Black Star" by Yngwie Malmsteen - This neoclassical metal song features Malmsteen's signature style of fast alternate picking, sweeping arpeggios, and scalloped fretboard techniques. It is a showcase of his mastery of the guitar.

Overall, the difficulty of a song depends on the player's skill level and musical taste. Some guitarists may find it easier to play complex technical passages, while others may excel in creating emotional melodies or improvising solos.